A pillow block bearing (or plummer block) is a pedestal used to provide support for a rotating shaft with the help of compatible bearings and various accessories. The assembly consists of a mounting block which houses a bearing. The block is mounted to a foundation and a shaft is inserted allowing the inner part of the bearing / shaft to rotate. The inside of the bearing is typically 0.001 inches (0.025 mm) larger than the shaft to ensure a tight fit. Set screws, locking collars, or set collars are commonly used to secure the shaft. Housing material for a pillow block is typically made of cast iron or cast steel.