block chain

from The Century Dictionary.

• noun A form of drive-chain for transmitting motion or power, in which the alternate links are solid blocks connected by side-pieces or links which are held in place by pins through the blocks near their ends.

from the GNU version of the Collaborative International Dictionary of English.

• (Mach.) A chain in which the alternate links are broad blocks connected by thin side links pivoted to the ends of the blocks, used with sprocket wheels to transmit power, as in a bicycle.