A block chain, also called a "bar-link" or "block-and-bar" chain, is a mechanical drive chain. It is composed of side plates, where each plate straddles one end of a block and is connected to the block with a pin going through a hole at one end of the block. Block chain is simple, but compared to modern roller chain is heavy and is less efficient rolling over sprockets due to the lack of rolling motion as the chain engages and disengages the sprockets. However, it has advantages in specific applications and while not dimensionally standard like roller chain, it is commonly used for specific applications, especially where no sprockets are needed, loads are very high and strength is greater concern than efficiency, and where the chain has special fixtures for holding or engaging a load[1]