Ten-pin bowling regulations, identification letters and numbers, and general wear from normal use. For much of the history of bowling, bowling balls were made using a three-piece construction method. Starting in the mid-1990s, however, most manufacturers switched to a two-piece method. In response to these innovative ball designs, the American Bowling Congress placed further restrictions on the technical characteristics of the ball such as the radius of gyration and hooking potential. A game of bowling consists of ten frames. In each frame, the bowler will have two chances to knock down as many pins as possible with their bowling ball. In games
Ten-pin bowling set by human pinsetters or "pin boys", but with the invention of the semi-automatic pinspotter in 1936 (usually just the "spotting table" component), the process became much easier. In 1946 AMF Bowling launched the first commercial fully automatic pinspotter, the AMF Model 82-10, followed closely by the more developed 82–30 model (still in common use in the 21st century) to replace the earlier Brunswick semi-automatic and fully manual bowling establishments. Brunswick itself introduced its own "Model A" automatic pinspotter design to bowling centers in 1955, and along with its successors (A2 and "JetBack", both with quicker delivery of returned balls