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(originally published to Helium writing site, now gone)

The rules of ten pin bowling are set down by the regulator in each country. In the US, this is the United States Bowling Congress, first established as the American Bowling Congress in 1895. All sanctioned leagues and tournaments must abide by these rules. The rules vary little between countries. Most of the rules are concerned with the playing area, the bowling balls used, and the pins, as well as rules relating to league and tournament play.

The playing area includes the lanes themselves plus the approaches. All lanes are 62 feet 10 3/16 inches in length. The distance from the foul line to the middle of the head pin, or 1-pin, is 60 feet, with a half inch tolerance, although the head pin must be 2 feet 10 3/16th inches from the end of the lane. The lanes can be between 41 and 42 inches wide and consist of 39 boards. These used to be made of maple and pine wood but are now synthetic.

There are small arrows about 15 feet down the lane, which are used as targets. The lanes are flat, to a tolerance of 40/1000th of an inch or one millimeter. Each lane has about 0.6 of an ounce of oil applied daily to protect it. For leagues and tournaments, this increases to around 0.8-1.0 ounce. The approach area must extend at least 15 feet back from the foul line. This area has two sets of dots about 12 and 15 feet from the line. These are used by bowlers to work out their starting spot.

Bowling balls must be between 26.7 and 27 inches in circumference and not exceed 16 pounds. There is no limit at the lighter end, although six pound balls are generally the lightest ball in most centers and used by young children. Balls must be free of marks and indentations, except for thumb and finger holes, manufacturer markings, and those through normal wear and tear.

The balls are made of a solid inner core and a non-metallic outer shell of rubber, polyester, or more recently, urethane, or reactive material. Modern bowling balls have a greater range of core densities and now have to be measured along three axes to ensure they comply with the rules and don’t give an unfair advantage: the x-axis which is a line through the ball parallel to the foul line, the y-axis which is a line parallel to the boards, and the z-axis which is the vertical line through the ball. Surface hardness must be at least 72 on the durometer scale.

Pins are made of maple wood coated with plastic 3/32nd of an inch thick. They are 15 inches tall and 4.766 inches in diameter at their widest point, which is 4.5 inches from the base, or where the ball makes contact. Diameter at the bottom is 2.031 inches. There are many additional measurements to make sure pins are a consistent shape. Pins must weigh between three pounds six ounces and three pounds ten ounces. The pins have one or two voids or cavities towards the bottom in order to balance the wider lower part with the narrower upper part; otherwise, the pins would be bottom heavy and wouldn’t fall properly.

The pins are configured in a triangle at the end of the lane. The headpin or 1-pin is in the middle and in front of the other pins. The second row has two pins, called the 2-pin and 3-pin (from left to right), the third row has three pins, or the 4-pin, 5-pin, and 6-pin, and the back row has four pins, or the 7-pin, 8-pin, 9-pin, and 10-pin.

A game of ten pin bowling is divided into ten parts or frames. A player has two opportunities to knock the pins down in each frame. If the bowler knocks all pins down with one ball, this is a strike (denoted by an X), and the bowler has completed this frame. If any pins are left standing after the first ball, the player has a second chance of knocking down the remaining pin or pins. If the remaining pins are knocked down with this second ball, the bowler is awarded a spare (denoted by a /). The next player or team member then has their turn, and so on, until everyone has bowled their first frame. The lead bowler then starts their second frame.

Each pin knocked over counts for one point. If a player bowls down six pins with the first ball and then another two with the second ball, they score eight for that frame. Where any pins are left standing after two deliveries, this is an open frame, and remaining pins are swept away by the sweep attached to the pinsetting machine. When a bowler gets a spare, the score for that frame equals the ten pins they knocked down plus the next shot. If the next bowl is a seven, the player achieves a score of 17 in the first frame, i.e. ten for the spare plus seven for the next ball.

When a bowler scores a strike, the number of pins they knock down with their next two deliveries is added to the value of the strike. Thus if the player follows a strike in the first frame with a six and a three in the second frame, their score in the first frame is 19, i.e. 10 + 6 + 3. The second frame score is 28, obtained by simply adding the six and the three to the first frame score. If the bowler strings strikes together, their score will go up by 30 a frame, i.e. the value of the strike plus the next two balls. A perfect score is thus 300.

There are various other rules laid down by the United States Bowling Congress and the bowling associations of other countries. Crossing the foul line at the start of the lane results in no score for the delivery, except if you hang onto the bowl, in which case you can have your shot again.

Leagues and tournaments have various rules such as those for tardy bowlers, blind scores for absent players, bowling on the wrong lane (the ball must be rebowled on the correct lane), the system of handicapping (unless a scratch competition), how many points a team earns if they win a game, and so on. Finally, there are some basic etiquette rules such as giving way to the bowler on your right and participating in a sporting manner.