A pillow block bearing consists of a mounting bracket (pillow block) that houses a bearing and is used in low-torque, light load applications.
With this configuration, the pillow block is bolted to a foundation, securing it, while the shaft and the inner ring of the bearing are free to rotate. Usually made of grey cast iron, pillow blocks come in two types, split or un-split. With split pillow blocks the housing element or cap can be separated from the base. An un-split pillow block is made from one solid piece.
Often, the terms pillow block bearing and plumber block bearing are used synonymously but the two are different devices. Both are designed to be mounted to a surface through mounting holes on the base of the block. They differ in that plumber block bearings do contain an inner bearing and they are also designed for higher loads and more corrosive environments.