The All England Lawn Tennis Club describes how they produce a grass court on their website: 1. The courts are built and planted in April, with nine tonnes of grass seed used each year. The courts will be trimmed after the new grass reaches 15mm, and then three times a week until May to maintain the same height. 2. The club's gardener starts work at around 3am and finishes by 6pm each day. He uses a motorized lawnmower, weed whacker, edger and sprayer. Wimbledon is one of the only Grand Slam tennis events that takes place on grass courts. This means that the players compete in a slow-moving game on an athletic field where the best hitters and runners are able to take advantage of mistakes on the part of their opponents. At the end of each match, the umpires inspect each player's footgear to make sure it meets the requirements for championship play. If any piece of footwear causes concern, the umpire will signal to the player involved who can provide an alternative shoe. The player must then change into these shoes before leaving the court. If a player fails to comply with this rule, then his or her score will not count and the opponent may choose to send him or her off the court immediately. There is a doctor on site who can evaluate any player who shows signs of injury and send them off the court if necessary. In this case, the player's score will not count either.