One-cushion is a distinct carom discipline, not a compulsory qualification before three-cushion. Its shorter contact requirement makes it useful for studying one rebound without pretending that every position is easy.
The scoring condition
UMB Article 82 requires the cue ball to contact a cushion before the second object ball. More cushions are allowed. The cushion may precede the first object-ball contact or fall between the two. A cushion touched only after both object balls is too late; the object ball's cushion contact does not satisfy the requirement.
Two routes to compare
Use A and B for the two object balls and C for a cue-ball cushion contact. A → C → B and C → A → B satisfy the contact-order condition, provided the stroke has no other foul. A → B → C does not. These are logical examples, not guaranteed playable trajectories or the opening-shot exception, which requires red first.
Build a small reference sheet
Choose a reproducible ball-first position. Before each attempt, predict the cushion contact and approach to B. Record contact order, arrival side and whether B was reached. Keep aim and spin fixed while comparing two comfortable paces. Then change only aim. Our exercise uses personal observations, not an official drill count or a promised score threshold.
Know what the exercise cannot prove
A single-ball rebound exercise is not a scoring carom. Mirror geometry is only an ideal reference; actual rebound depends on spin, pace and equipment. Stop to check the rules for touching balls rather than inventing a three-foul reset. A match uses its own point target and ending rules; a practice success is not a universal competition average.
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