Couplers are a parallel thread mechanical splicing system designed for the connection of concrete reinforcing bars from 012~050. Mechanical couplers to splice reinforcing bar has been regarded as a means of reducing the use of long bars and reduce wastage of expensive rebar's due to Splice lapping of the ends in the conventional methods of joining rebar's. More recently, engineers and installers have recognized the benefits of using couplers to increase construction speed, improve productivity and simplify design details.