Winsurfing is a surface water sport using a windsurf board, also commonly called a sailboard, usually two to five meters long and powered by a single sail. The rig is connected to the board by a free-rotating flexible joint called the Universal Joint (U-Joint). Unlike a rudder-steered sailboat, a windsurfer is steered by the tilting and rotating of the mast and sail as well as tilting and carving the board. This method of controlling the board's direction is called the free-sail system.