Ten-pin bowling ball contacts only the 1, 3, 5 and 9 pins; for a left-hander, the 1, 2, 5 and 8 pins. In order to count, a pin must be knocked over entirely. If the pin is wobbling as the automatic pin machine picks it up (or the machine itself knocks over the pin while it is wobbling), it is still considered standing and is not scored. Also, if a pin is moved, it does not change its designation. For example, if the 10 pin were still standing and the 7 pin slid into the 8 pin position, converting this spare would
Ten-pin bowling if synthetic. The top of the pin shall have a uniform arc with a radius of . The USBC also has regulations governing the weight distribution of the pin from top-to-bottom. Pins are allowed one or two "voids" (holes) in the belly area (which can be viewed if the pin is cut in half from top-to-bottom). The voids are needed to balance the narrower top half of the pin with the wider bottom half. Without them, the pins would be too bottom-heavy to fall properly when struck. In addition, a standard regulation pin may lean no more than 10 degrees