The Standard Upset Parallel Thread Couplers offer a full strength connection. Each end of the bar to be joined should be square and is enlarged using a cold forging process. The rebar ends need to be clean and square to allow for a close rebar to rebar connection within the coupler. If the end face is not square or even after upsetting, then the head shall need to be cut off and re-upset. A parallel metric thread is then cut onto the enlarged bar end. The thread form is such that the cross sectional area of the bar ends is not reduced, thus ensuring the strength of the connection matches or exceeds that of the parent bars.