Mechanical couplers, also known as mechanical splices, are used to join lengths of rebars together. Building code requirements for masonry construction now require longer lap lengths for some bar sizes.
These changes mean more congestion in masonry cells and more difficult construction. To alleviate this problem, builders can either use open-cell blocks, which are more expensive, or use mechanical couplers to eliminate the lap. Couplers are designed to splice the same diameter bars where one bar is free to move and can be rotated.