30" x 10" Lightweight Polystyrene Knee BoardsLightweight Polystyrene Knee Boards measure 30 In. x 10 In. and are made from tough, heavy duty polystyrene plastic. These concrete sliders have rounded edges to prevent digging into concrete. The polystyrene prevents corrosion and allows easy use of boards with plastic that is easy to clean. The white material is non marking. Toe bracket secures the foot and allows for ease of back and forth movement along the work surface. Each board has an