Ten-pin bowling ramp in which a bowler will use two hands and push the ball down the ramp onto the lane. There are three widely recognized delivery styles used while the ball is released onto the lane. (See article: Bowling form.) These are the "stroker", "cranker" and "tweener" styles. Lesser used (and newer) styles include "no-thumb" and "two-handed". Strokers often keep their shoulders square to the foul line and their backswing generally does not go much above parallel to the ground. This type of delivery reduces the ball's rate of revolution, thus decreasing its hook potential and hitting power. Strokers rely on
Ten-pin bowling it is damaging the integrity of the sport. Before 1970, nearly all bowling balls had a hard rubber surface. As the coatings applied to wood lanes changed from softer lacquer to a harder urethane in the early 1970s, the first polyester balls became widely available. Subsequent changes since the early 1980s — particularly with urethane surfaced and later "reactive" resin or composite ("particle") surfaced bowling balls—have been altering the physics of how the ball rolls and strikes the pins. Coupled with synthetic lane surfaces and advanced oiling machines presenting the opportunity to lay out lane oil patterns that make targeting