A bowler reaches his delivery stride by means of a "run-up" and an over is deemed to have begun when the bowler starts his run-up for the first delivery of that over, the ball then being "in play". Fast bowlers, needing momentum, take a lengthy run up while bowlers with a slow delivery take no more than a couple of steps before bowling. The fastest bowlers can deliver the ball at a speed of over and they sometimes rely on sheer speed to try to defeat the batter, who is forced to react very quickly. Other fast bowlers rely on a mixture of speed and guile by making the ball seam or swing (i.e. curve) in flight. This type of delivery can deceive a batter into miscuing his shot, for example, so that the ball just touches the edge of the bat and can then be "caught behind" by the wicket-keeper or a slip fielder. At the other end of the bowling scale is the spin bowler who bowls at a relatively slow pace and relies entirely on guile to deceive the batter. A spinner will often "buy his wicket" by "tossing one up" (in a slower, steeper parabolic path) to lure the batter into making a poor shot. The batter has to be very wary of such deliveries as they are often "flighted" or spun so that the ball will not behave quite as he expects and he could be "trapped" into getting himself out. In between the pacemen and the spinners are the medium paced seamers who rely on persistent accuracy to try to contain the rate of scoring and wear down the batter's concentration.
