A free kick or penalty in football, a free throw in basketball, and a serve in tennis are all instances of closed skills. These abilities are performed in a steady, predictable setting, and the athlete is aware of the exact sequence of motions that must be performed. Closed skills are easy to learn and require little or no strategy to perform. Open skills on the other hand are unpredictable actions that may be accomplished with either foot, thrown or punched, struck or kicked, carried out while running or standing still. Open skills can vary greatly in difficulty and require considerable practice to perfect them. For example, an open skill is throwing a ball; a close-knit ball of leather with strings attached, which an athlete uses his arm to fling through the air to hit a target at least 10 feet away. Closed skills are used in games where accuracy is important, such as golf, tennis, and bowling. Open skills are useful in sports that require quick reflexes such as soccer, basketball, and American football. The difference between these two types of skills is important because it tells us how to improve each one. If we want to become better at throwing a ball, for example, we need to work on our technique - how to fold the elbow when throwing and where to place the thumb when catching. This type of training will help us develop stronger muscles around the shoulder area and give us more control over the projectile.