Combination Shots
Driving one object ball into another to pocket the last ball in the chain, and knowing when the odds are worth it.
What a combination is
In a combination shot the cue ball strikes your first object ball, which in turn strikes a second object ball and sends it to the pocket; longer chains push a third or fourth ball as well, but the last ball in the chain is the one you are trying to make. The useful way to picture it is that each ball in the chain has to act like a cue ball for the next one: the first object ball must arrive at the exact contact point on the second ball that would send it to the pocket, just as the cue ball normally would.
Aim the chain backward, and expect errors to multiply
Aim a combination the same way you read any cut: start at the pocket, work back through the last ball to find the ghost-ball contact point it needs, then treat that as the target the previous ball must be driven into, repeating back up the chain to the cue ball. The catch is that every contact adds its own margin of error, and those errors compound down the line — so a two-ball combination is meaningfully lower percentage than a direct shot, and each extra ball lowers the odds again. When a makeable direct shot exists, it is almost always the better choice.
Dead combinations and frozen balls
The big exception is a "dead" combination, where two object balls are frozen together (touching): the second ball is driven straight along the line drawn through both ball centers, almost regardless of where the first ball is struck. If that line of centers points into a pocket, the combination is nearly automatic and well worth taking. When the balls are separated rather than frozen, contact-induced throw can nudge the second ball off the pure geometric line, so hit the first ball close to center with controlled speed and avoid unnecessary English to keep the transfer predictable.