How can you tell if a shot is a double hit or not?
The following videos explain and illustrates how to detect and avoid a double hit in various situations:
For more information, see NV B.2 – Mike Page’s double hits, push shots, and frozen balls and “Rules – Part II: double hits” (BD, September, 2009). The HSV DVD also has a nice feature on this. Also, many example shots, with explanations for the appropriate rulings, are available here:
For more information, see the Pool Rules Quiz resource page.
Clips HSV A.110-A.115 also show the effects of speed, cue stick elevation, and follow-through on double-hit avoidance for a chalk-width gap between the CB and OB. Unfortunately, clips A.110-A.112 and A.113-A.115 are from different viewpoints and were shot by different shooters with different amounts of follow-through, but the results are interesting nonetheless. Notice that the cue stick nudges the CB in mid air (i.e., the shot is a foul) in the 3rd (fast) stroke of A.112. This one is tough to call even with the high-speed camera.
Here an example elevated-cue small-gap foul by Shane VanBoening. If the CB was not frozen to the 10, the shot was most definitely a foul. The CB goes forward way too much before drawing back. With the balls not frozen, this cannot happen without a double hit. You can even hear the double-hit ferrule-slapping sound in the video (although, audio alone is not appropriate evidence for calling a foul). With a clean hit on this shot, the CB would have come off the tangent line of the 10 into the 14, the 14 would have moved more, and the CB would have drawn back without going forward very much at all (if any).
A video from Tony Christianson on FaceBook is another interesting example of small-gap elevated draw shot that is a foul, but is tough to call (even with slow-motion-replay video). From the slo-mo video evidence, this shot is a foul. With a ball gap that small, the cue would need to be elevated much more to cause the CB to go that much forward with a legal hit (in which case it would also go much higher). If you put your cursor on the CB a gap-width inside the front edge, it looks fairly clear that the tip and ferrule go too far forward during the shot, causing a double hit. The double hit is not visually obvious, but the action of the CB seems to imply a foul. For a ref watching this shot live, a foul would be hard to call. Even with the slow-motion video evidence, the call is disputable because the evidence is not very strong. In these situations, the benefit of the doubt goes to the shooter.
Sometimes a double hit is not a foul. If there is no clear evidence of a double hit based on observation of the motion of the balls, then the shot is considered legal. Here’s an example:
For more information, see: “Legal Fouls” (BD, November, 2016).
The following videos show some interesting methods that can be used to avoid a double hit when there is only a small gap between the CB and OB:
- NV B.49 – Using your knuckles to prevent a double hit and stop the cue ball, with Bob Jewett
- NV B.50 – Using your knuckles to prevent a double hit and get follow, with Bob Jewett
- NV B.51 – Using your natural forward stroke limit to prevent a double hit and get draw, with Bob Jewett
- NV B.52 – Using a fouetté shot to prevent a double hit, with Bob Jewett
Here’s some slow-motion footage of various fouetté shots:
For reference, here’s WPA rule 6.7 that defines a double hit foul:
6.7 Double Hit / Frozen Balls
If the cue stick contacts the cue ball more than once on a shot, the shot is a foul. If the cue ball is close to but not touching an object ball and the cue tip is still on the cue ball when the cue ball contacts that object ball, the shot is a foul. If the cue ball is very close to an object ball, and the shooter barely grazes that object ball on the shot, the shot is assumed not to violate the first paragraph of this rule, even though the tip is arguably still on the cue ball when ball-ball contact is made.
However, if the cue ball is touching an object ball at the start of the shot, it is legal to shoot towards or partly into that ball (provided it is a legal target within the rules of the game) and if the object ball is moved by such a shot, it is considered to have been contacted by the cue ball. (Even though it may be legal to shoot towards such a touching or “frozen” ball, care must be taken not to violate the rules in the first paragraph if there are additional balls close by.)
The cue ball is assumed not to be touching any ball unless it is declared touching by the referee or opponent. It is the shooter’s responsibility to get the declaration before the shot. Playing away from a frozen ball does not constitute having hit that ball unless specified in the rules of the game.