Detecting and Avoiding Double-Hit Fouls

based on the World Pool-Billiard Association (WPA) World Standardized Rules (the “official rules of pool”)

How can you tell if a shot is a double hit or not?

See:

The following videos explain and illustrate 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 are some good super slow motion video examples both elevated and level-cue shots with and without double hits:

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.

Here’s another good small-gap elevated-cue example from the 2021 US Open. If the balls were frozen, this shot would have been legal based on the info and examples of the frozen-CB resource page. However, there was a small gap here and a double hit did occur based on the motion of the CB, but the referee made the wrong call.

Here’s another example of a blatant double hit foul against Efren that the experienced referee and commentators got wrong. The CB obviously went forward of the tangent line immediately due to the double hit.

Here’s an example of Shane VanBoening using the mechanical bridge, where the audio during slow-motion replay seems to suggest a secondary hit on the CB, but there is no clear visual evidence of a foul. Using audio to attempt to call a foul can be dangerous since it can be misleading. If there is no clear visual evidence of a foul, a foul should not be called.

Here’s another interesting shot that is tough to call. It is a nearly-vertical 1-mm gap jump shot by Larry Nevel. This shot is a foul because there is no way for the CB to jump straight up and then go forward that much without secondary contact. However, some referees might not call a foul on a shot like this because the visual evidence is not very clear (without super-slow-motion video instant replay, which would clearly show the secondary contact). Sometimes, highly elevated jump shots are not fouls. For example, see HSV B.19 – Highly elevated cue jump shots, where the foul is very close.

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. A good example is an elevated follow shot, where secondary hits are often obvious based on the distinctive straight trail of chalk marks on the CB after the hit:

For more information, see: “Legal Fouls” (BD, November, 2016). Other examples of shots that are fouls (if viewed with super-slow-motion video) but aren’t called fouls are fouetté shots and highly-elevated jump and massé shots, as demonstrated in these videos:

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:

And here are some additional techniques:

  • Hold your cue about an inch behind its balance point and hit the top of the CB using an open bridge. The cue easily pops up, clearing the double hit.
  • Put your grip hand thumb through a belt loop to limit the cue’s forward motion.
  • Brace your grip hand behind and against your hip or body to limit and stop the forward motion of the cue.
  • Illegal idea: Place the cue tip under the front edge of the CB and lift the cue straight up. Unfortunately, this is not a legal stroke (since the cue is not going forward in the direction of the cue).

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.

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