The most specialised position in the field is the wicket-keeper. They are required to stand behind the stumps at all times, fielding the ball both from the bowler and the fielders. They are allowed to wear padded gloves and will often help the captain and bowler set fields.
There are three forms of dismissal that the wicket-keeper plays a part in. Firstly, they will often take catches behind the wicket if a batsman has hit the ball. They can stump a batsman by breaking the wickets if the batsman strays from his crease even if he has not hit the ball and they will usually be required to effect run outs, which is breaking the stumps before a batsman can complete a run.
Wicket-keepers must be fit and agile as they are required to constantly move between the stumps and their starting position, which for a fast bowler, can be a long way back.