Some engines have flat steel plates attached to each end of the cylinder block.
End plates add rigidity to the block and provide a mounting surface for parts such as gears, blowers, pumps, and generators. In the majority of large engines, a base is used to support the cylinder block. Not only does the base support the cylinder block but it also provides a mounting surface for accessories to the engine and serves as a reservoir for the lubricating oil used by the engine. Many of the smaller engines do not have a separate base. Instead, they have an oil pan, which is secured directly to the bottom of the block.