A type of bowling very popular in Baltimore and virtually unknown everywhere else in the world (I may be wrong, but I've never seen a duckpin alley more than thirty miles from Baltimore)*.
Duckpin bowling differs from ordinary, tenpin bowling in the size of the balls and pins. A duckpin ball is much smaller than a tenpin ball, about five inches in diameter and weighing only a few pounds. Because of its small size, it can be held comfortably in a cupped hand and no holes are drilled into it. The pins are much smaller and lighter than tenpins, although their number (ten) and arrangement are identical to tenpins.
The only significant difference in the rules of play is that a duckpin bowler gets three, rather than two, throws per frame. The scoring of strikes and spares follows the ordinary rules, but a player receives no special bonus for completing the frame on the third roll.
Duckpin balls can be thrown much harder than tenpin balls. This is what makes the game fun! However, their small size makes throwing strikes much more difficult. Spares can actually be easier in ducks under certain conditions, particularly splits. A tiny duckpin hit by a fast-moving ball can fly like shrapnel, ricocheting off walls and covering a much greater area than a tenpin. In duckpins, a spare conversion of the notorious seven-ten split is a real possibility, one that I accomplished twice as a twelve-year-old league bowler. Scoring is much lower than in tenpins, though, and a perfect 300-pin game is unheard of.
*Although kot13 reports seeing one in Connecticut, a region better known for candlepins.