Mechanics of the Rock · Chapter 3
The same kick that quietly scores in APA league can end your inning in CSI 8-ball. This episode separates the geometry you can trust from the systems that need an adjustment, and maps what every major ruleset does with the same bank shot.
One cushion between cue ball and pocket. Every ruleset has a different idea of what that’s worth.
01 — What this episode is
Banks and kicks are where league instincts are most expensive, because the shot is the same everywhere and the rules around it are not.
A bank and a kick are the same physical event: a ball driven to a cushion before it goes where you intend. A bank sends an object ball off a cushion toward a pocket. A kick sends the cue ball off a cushion to reach a target. The geometry does not care which ruleset you are playing. The verdict does. In APA 9-ball a kicked ball that drops counts, no call required. rule 3 In CSI 8-ball the same shot is not obvious by definition, and an uncalled drop ends your inning. rule 2 In bank pool the kick can never score at all. rule 5
The premise of this episode, verified in the source corpus: one-rail and multi-rail diamond systems are calibrated reference methods, not exact solutions on a real table. The corpus supports that from both directions. The measured tier contains real table validation for exactly one system, 12 with documented shortfalls on others. 12 The instruction tier is explicit that adjustments are part of practice. instructional 11 So every system here is presented with its standing, not as a law.
A cross-side bank goes off a long cushion into a side pocket; a cross-corner bank goes off a long cushion into a corner; a straight-back bank goes off an end cushion. A double kiss is the cue ball re-contacting the object ball into the same pocket, and in bank pool it is the deal-breaker. Definitions per the OnePocket.org appendix and the WCBS glossary. secondary 6 20
02 — One rail
Every one-rail system you have heard of is the same geometry, and none of them is a law.
The family is one construction wearing different clothes. Dr. Dave: the mirror kicking system "is a visual application of the classic 2-to-1 system," with the equal-distance and midpoint-parallel-shift systems delivering "the same aim point on the rail." instructional 14 For banks, the same construction runs in reverse: "the target is the pocket (instead of the OB), and you measure from the OB (instead of the CB). Everything else is the same." instructional 14
Diamond counting is table-relative, so the construction reads the same on a bar box. What changes is the cushion: the measured tier found the 7-foot Diamond bar box banking almost a diamond short of system. measured 12 Section 03 carries the numbers.
Speed shifts the reference line itself, and the corpus gives the mapping verbatim: "For slow-speed shots where the target is a medium-to-long distance (2-4 diamonds) from the kicking rail, you measure along the line of diamonds. For medium-speed shots or when the target is closer to the rail (1-2 diamonds), you measure along the center of the cushion… And for fast-speed shots or when the target is very close to the rail (less than 1 diamond), you measure along the rail groove." instructional 14 The lab above runs that mapping: the same kick aimed at the same 2-ball touches the cushion 3.7 inches apart depending on speed.
The object ball is not the cue ball. For kicks, the vertical spin that matters at the cushion belongs to the cue ball, which you control with tip position. For banks, it belongs to the object ball, which you control only through speed: "harder = less or no forward spin; softer = more forward spin. This is also why hitting harder shortens bank angles." instructional 10
Cushion efficiency sets the ceiling. The twice-plus-tenths technical proof models a cushion with a 0.7 coefficient of restitution, a rolling ball keeping about 70% of its perpendicular speed off a typical cushion. measured 22 The 0.7 is a modeling constant, not a manufacturer specification, and it is flagged in section 09. The cushion is also alive in another sense: "The cushion imparts spin (and can even reverse the spin direction) on a kicked or banked ball," which is the documented mechanism behind the twice-across banks you see from Reyes and Gorst. instructional 10 15
Spin and speed interact in documented directions: more speed shortens a rebound and less speed lengthens it, with one documented exception where the effects balance out; running spin lengthens, reverse spin shortens; sidespin matters little at shallow angles into the rail but has a large effect off the second rail; and an outside cut transfers spin that shortens a bank while an inside cut lengthens it. instructional 10 For a feel of magnitude: one third, two thirds, and full maximum spin move a straight-into-the-cushion kick by roughly 1, 2, and 3 diamonds, a forum-sourced rule of thumb republished by Dr. Dave as an approximation. anecdotal 10
Cutting a ball that is already against the cushion has its own geometry, because the cushion interferes with the cut. The documented baseline: "ignore the cushion and just aim the shot normally." The cushion enters the shot only on very large cuts, where a cushion-first hit with running spin helps pocket the ball. instructional 16
03 — Firm banks
When the object ball reaches the cushion without natural roll, the mirror hands the job to a different family of systems.
Firm hits and near-rail banks arrive at the cushion sliding, and the sliding-bank family covers them: twice-plus-tenths at 2.2 times the object-ball distance, measured along the rail grooves; one-third-more-than-twice, 2x + 1/3, also along the grooves; one-more-than-twice, measured through the diamonds, which "requires adjustments" at larger angles. instructional 14 Dr. Dave's comparison of the two leading systems: "The systems provide very close to the same lines of aim for small-to-medium-angle banks. At larger bank angles, above the (5+1/3)-to-2.5 line, the '1/3-more-than-twice' system aim will tend to make the ball bank a little short of target." instructional 14 Both work for sliding banks: fast speed, or an object ball close enough to the rail that it has no time to develop forward roll. instructional 14
| System | Rule of thumb | Measured along | Standing in the corpus |
|---|---|---|---|
| Twice-plus-tenths (TPT) | 2.2 × the object-ball distance | Rail grooves | Validated against measured tables 12 |
| 1/3-more-than-twice | 2x + 1/3, starting 1/3 diamond above the 2-to-1 line | Rail grooves | Matches TPT on small-medium angles; tends short above (5+1/3)-to-2.5 14 |
| 1-more-than-twice | 2x + 1 | Through diamonds | Needs adjustments at larger angles 14 |
| Eckert reference lines | 2x-to-3/4x through-diamond | Through diamonds | Memorized no-math reference lines 14 |
The measured tier. TP B.28 is the only place in the corpus where a sliding system meets real tables: "1) The twice-plus-tenth system matches measured data very well on typical tables under typical conditions. 2) The 9' Olhaussen and 7' Valley tables banked very close to 'on system.'… 3) Diamond tables (9' Red Label and 7' bar box) banked very short, especially at larger bank angles… 4) The 7' Diamond bar-box banked almost a diamond shorter than typical 'on system' tables!" measured 12 The proof prints its own caveat: the non-Olhausen tables were measured "under slightly humid conditions, with old, worn-in cloth." measured 12
The Diamond mechanism follows from the cushion, not the slate: Diamonds use Artemus cushions, which are very bouncy, and their cushion noses are often lower and angled down slightly, so the ball rebounds with more perpendicular speed, creating "a shorter rebound and more retained speed." instructional 11 The blanket warning from the same source: "Standard kicking and banking systems work fairly well on most pool equipment; although, adjustments will be required based on table conditions," and Diamonds "play much shorter and faster than all other table brands." instructional 11 The user-sourced correction magnitudes, republished by Dr. Dave: about 10% of the aim for the 2-to-1 and Corner-5 systems, and a quarter diamond for the Plus System. instructional 11 This is not a corner case for the anthology reader: premier US events, including BCAPL Nationals and APA Worlds, are played on Diamonds. observation 21
Pocket jaws scale with the table; the ball does not. The same facing-versus-back read applies on a bar box, with slightly less room between facing and back.
Double kisses are the bank pool deal-breaker: the object ball is spotted and the inning is lost. secondary 6 The test in the lab is Freddy "The Beard" Bentivegna's, published on Dr. Dave's page, including the steep cross-over case: when the line through the cut point continues into the middle of the pocket's back, the kiss is on; when it aims at the short rail, "you can go ahead and shoot the shot with impunity." instructional 15 The avoidance toolbox: speed and transferred spin, hopping the object ball, and the observation that faster speed reduces double-kiss exposure. instructional 15
That is one reason top bankers use speed: "With faster speed, there is much less variation from table to table and from shot to shot," less forward roll into the rail, and less forward curve after rebound. The priced trade-off is printed with the advantage: "A disadvantage of faster speed is the reduced effective 'size' of the pocket," with the documented exception that on two-way shots, pocket speed is the choice. instructional 15 And speed controls the bend problem: the $2,000 Bank Bend Challenge exists because "the amount of bend possible on typical shots on typical equipment is much smaller than many people think is possible." measured 15
04 — Corner-5 and the ledger
The three-rail systems are calibrated references with arithmetic for bones. The honest question is not whether they are exact. It is what they are exact for.
Corner-5 is the workhorse for three-rail kicks off a long rail. From the technical proof: "The Corner-5 diamond system is a formula-based method that can be used to aim multiple rail kick shots. Unlike with some other bank and kick shot systems, you use running English and aim directly through the diamonds." instructional 13 The formula: the third-rail target T equals the originating number D minus the first-rail number F. The proof's own worked example: "the originating direction number (D) is 4.5 and the first rail number (F) is 2. Therefore, the ball heads toward the third rail number (T) of 2.5 because: 2.5 = 4.5 − 2." An alternative numbering, T = D'/2 − F + 1, trades fractions for arithmetic. instructional 13
Corner-5 counts diamonds, which are table-relative, so the numbers hold. Diamond-brand tables still need the down-table correction from section 03: about 10% of the aim. instructional 11
The system's own admission is in its diagrams: TP 7.2 annotates the third rail with fast, medium, and slow speed marks, which is the proof acknowledging that speed moves the impact point around the target. instructional 13 Dr. Dave's adjustment article exists for the same reason and is entirely devoted to the corrections. instructional 23 A calibrated reference with a documented spread is still useful. It is just not a solution.
The rest of the family, briefly. The Plus System is "used mostly for aiming two-rail kicks off a short rail, but it can also be used to aim three-rail kicks off a long rail," with a quarter-diamond adjustment documented for Diamond tables. instructional 14 11 Tom Ross's two-rail midpoint-parallel-shift needs "no calculations" but a standardized stroke: "you must deliver a consistent stroke with one tip of english," calibrated by his benchmark shot through the center diamond. instructional 18 Its scope is bounded: "the system will work consistently for any two rail kick on the same half of the table." instructional 18 Dr. Dave's version adds the effects: "OB close to cushion goes short, so aim farther from pocket; OB far from cushion goes long, so aim closer to pocket," and two-rail banks tend long, especially steep into the first rail. instructional 14 His April 2014 column says the midpoint kick "will typically go longer than predicted by a true parallel shift," so adjust toward the pocket. instructional 24 Jewett's assessment of the naive two-rail mirror is blunter: it "lets you see immediately how pitifully awful the two-rail mirror system is." instructional 14 The Sid System earns the same honesty: "the numbers on the second rail are off a little but as listed they are easy to remember." instructional 14
If you would rather skip arithmetic entirely: spot-on-the-wall systems replace it with an off-table landmark, placed about as far from the first rail as the cue ball travels after it; beyond three rails the convergence is narrow enough that any distant spot works. instructional 14 The Magic Spot is the fixed three-rail variant, and the Sixes System correlates the first leg's diamond separation with the fourth-rail convergence. anecdotal 14
| System or claim | Mathematical standing | What the sources say |
|---|---|---|
| Mirror / equal-angle (ideal) | Exact for an ideal cushion: frictionless, non-compressing, sliding ball, no spin | Geometric definition; real-shot variation is all adjustment 12 22 |
| 2-to-1 with a rolling ball | Reference only; needs the speed-and-distance line shift | Slow: diamonds; medium: cushion nose; fast: rail groove 14 |
| Shallow-angle kicks | Mirror fails; the contact-point mirror restores it | About a 70% rebound factor, rolling 14 |
| Corner-5 | Calibrated for a rolling cue ball with running english; speed marks in its own diagrams | T = D − F 13; adjustments article 23 |
| Plus System | Empirical; quarter-diamond adjustment on Diamonds | 14 11 |
| Two-rail midpoint shift | Visual construction; same-half scope; benchmark spin; tends long | 14 18 24 |
| Twice-plus-tenths (sliding banks) | Measured across five tables; best-performing sliding-bank system | "Matches measured data very well" 12 |
| Speed, spin, and condition corrections | Not exactable; condition-dependent, learned per table | "Provide a point of reference only" 10 |
Nothing in the authoritative instruction corpus claims a diamond system is exact on a real table. The measured tier exists only for twice-plus-tenths' validation and the Diamond-short findings; everything else is instructional practice plus documented adjustments. Treat every system output as an initial aim, then let speed and feel close the gap. synthesis 10–15
05 — Kick safeties
When you are hooked, the kick safety is the shot that keeps you in the game. Two named shots do most of the work.
Tom Ross states the convention and its limit: "Usually a good rule of thumb to follow is not to kick at balls that can be hit directly," with the documented exception: "in certain situations with an available direct hit, the rail-first kick can be the best option," the primary element being "a ball that's close enough to the rail to make hitting it a sure thing." instructional 18 The exception is not theoretical. His named case is Karen Corr's 2005 WPBA U.S. Open final safety against Allison Fisher: rail-first behind the 1, to "leave the two balls at opposite ends of the table with the 1 hidden behind the 9." instructional 18
The slide zone is about six inches on any table. Bar-box rebound is livelier, and Diamond bar boxes bank short, so aim the kick slightly closer to the ball than the geometry says. instructional 11
The mechanism, verbatim: "In that area known as the slide zone, a ball that bounces from a cushion at angles between 90 and about 45 degrees will rebound with no spin at all for the first six inches or so regardless of any spin it had going into the cushion. So, whenever we can come in behind an object ball in that zone to hit it full, the sliding cue ball will stop after knocking the object ball away." instructional 18 Execution notes: below-center hits "rebound more sharply from the rail. Thus you will need to aim at the rail slightly closer to the… ball than you may guess initially"; a little english away from the ball helps stop the cue ball; beyond about half a table, use a high hit instead of draw. instructional 18
Verkruyse names the two kicks the lab shows. The stop: "make sure that we make a full hit on the… ball… hit this shot about one tip above center ball… This will help the cue ball stop dead in its tracks." The kick-run: "when the cue ball hits the rail spinning backwards it reverses as it comes off the rail and has forward spin. This will make the cue ball spin down behind the wall of balls." instructional 19 His three reminders cover both: hit the object ball full; topspin stops the cue ball and sends the object ball away; draw reverses off the rail and runs the cue ball forward after contact. instructional 19
The tournament logic underneath: "Because ball in hand is the most powerful, offensive weapon in pool, we learn to play safeties that will stump our opponents. And, when we are hooked, we want to play kick shots that will not relinquish ball in hand. Professional 9 ball has evolved to a point where those two elements have become the crux of the game." instructional 18 One adjustment transfers with you: the two-rail midpoint kick typically goes longer than a true parallel shift, so aim toward the pocket. instructional 24
Under WPA and CSI ball-in-hand-anywhere fouls, the quality of a kick safe matters less than not fouling: there is no positional way to punish a legal kick. Under APA's no-push handicapped 9-ball and CSI's push-out games, kick safeties that leave instant offense are the documented escapes. synthesis 18 19 21
06 — The rules layer
The shot does not change across formats. What it scores, what you must say, and what a miss costs change completely.
The pattern in one paragraph. APA polices the safety boundary, not the kick: the glossary defines the kick, safeties must be marked, and two-way shots are policed. rule 3 WPA runs on a general confusion clause plus specific calling rules for 10-ball, and ACS adopts the WPA rules. rule 1 4 CSI defines the kick shot precisely and defines banks and kicks as not obvious. rule 2 Bank pool flips the economy to points: cushions in order, exact calls, fouls that cost balls. rule 1 2 5
| Format | Call required? | An uncalled bank that drops | Do kicks score? |
|---|---|---|---|
| APA 8-ball | No, only the marked 8 | It counts 3 | Yes 3 |
| APA 9-ball | No | It counts 3 | Yes 3 |
| WPA 8-ball | Yes, call shot with a safety available | Called ball only 1 | Called ball only 1 |
| WPA 9-ball | No | It counts 1 | Yes 1 |
| WPA 10-ball | Ball and pocket, no safety call | Opponent chooses who shoots next 1 | Only as called 1 |
| CSI 8/9/10-ball | Yes: banks and kicks are never obvious | Inning ends; opponent accepts position 2 | Only as called 2 |
| ACS | Plays the WPA rules | As WPA 4 | As WPA 4 |
| Bank pool (WPA / DCC) | Ball, exact cushions in order, pocket | Does not count 1 | Never 5 |
Verdicts are table-independent. The geometry underneath is not: section 03 carries the Diamond correction.
Count cushions out loud in bank pool. WPA requires the cushions "in order"; DCC requires "the exact number of cushions," and "short rails do not count." A correct bank to the wrong rail count is not a score. rule 1 5
07 — On the table
A short checklist, each item traceable to its section and tier.
08 — Conclusions
Six findings. Each names its evidence; where the evidence is thin, the finding says so.
The one-rail systems are one geometry under several names, instructional 14 and the corpus's own speed mapping, shallow-angle factor, and spin effects move the answer away from any single line. instructional 10 14 The system gives you the first aim; speed and feel finish it.
Twice-plus-tenths, validated on a 9-foot Olhausen and a 7-foot Valley, with documented shortfalls on Diamonds, the 7-foot bar box almost a full diamond short. measured 12 No other system in this episode has a measured counterpart.
The mechanism is documented (Artemus cushions, lower noses) instructional 11 and the shortfall is measured, measured 12 while the correction magnitudes, about 10% of aim and a quarter diamond, are user-sourced figures republished by Dr. Dave. instructional 11 Since premier US events are played on Diamonds, observation 21 this is the adjustment most likely to matter to you.
Corner-5's proof annotates speed-dependent landing marks in its own diagrams instructional 13 and a whole article exists for its corrections, instructional 23 while the two-rail family carries documented long and short biases and a two-rail mirror described as "pitifully awful." instructional 14
The slide zone, the stop kick, and the kick-run form one mechanism: spin state at the cushion decides what the cue ball does after contact. instructional 18 19 The six-inch figure is the instructor's approximation, not a measurement. unverified 18
Kicked balls count in APA, need calls in CSI and in 10-ball, and cannot score in bank pool. rule 1 2 3 5 The geometry transfers between formats; the verdict does not.
09 — Sources
Every claim in this episode traces to one of these sources. Numbering follows the research corpus's stable order; gaps are intentional.
These claims appear in the research corpus but did not survive verification against a primary source. They are printed where relevant with the unverified tag; they are collected here so the gap is impossible to miss.