The playing surface is an alley, or lane, approximately 78 feet long and 41 to 42 inches wide. On either side of the alley are gutters; if the ball goes off the edge of the alley, it will drop into the gutter and be carried past the pins. The approach is an area 15 feet long, ending at the foul line. The bowler, in making the approach, must not step over the line; 60 feet beyond it is the headpin. The pins are arranged in four rows, with one pin in the first row, two in the second, three in the third, and four in the fourth. They are numbered as shown in the diagram; the pins themselves don't carry specific numbers, but the spots on which they are placed do.
The regulation pin is made of hard maple; it is 15 inches high and has a diameter of 2 ¼ inches at the base and a circumference of 15 inches at its widest point. Weight must be between 2 pounds 14 ounces and 3 pounds 10 ounces. The regulation ball is of solid composition, has a circumference of no more than 27 inches, and weighs 10 to 16 pounds. A ball may have two or three finger holes; most bowlers use the three-holed ball, inserting the two middle fingers and the thumb into the holes.
Bowling in ordinary shoes isn't permitted, because it can damage the lanes. The peculiarities of the sport demand an unmatched pair of shoes. The right-handed bowler wears a left shoe with a relatively slippery sole, usually of hard leather or vinyl, and a right shoe with a rubber sole that will help "brake."
A game, or "string," is made up of 10 frames. Each frame represents one turn for the bowler, and in each turn the player is allowed to roll the ball twice. If the player knocks down all the pins with the first roll, it is a strike; if not, a second roll at the pins still standing is attempted. If all the pins are knocked down with two balls, it is a spare; if any pins are left standing, it is an "open frame."
If a bowler commits a foul, by stepping over the foul line during delivery, it counts as a shot, and any pins knocked down are respotted without counting. If pins are knocked down by a ball that has entered the gutter, or by a ball bouncing off the rear cushion, they do not count, and are respotted.