There are two basic methods by which jack-up rigs are supported during drilling operations. Mat-supported jack-up rigs consist of three or more legs that are connected at their lower ends to a large horizontal mat. The operating procedure involves floating the platform to the desired location and then jacking the mat toward the seafloor until the drilling platform is entirely supported by the mat. The platform may then be lifted to the desired operating height above the water level. The rig weight is distributed over a large area of the seafloor and thus mat-supported jack-up rigs can operate in a wide range of bottom conditions. They are particularly well suited for use on shallow water, soft mud areas and marginal fields