Abstract: A mechanical coupler for the reinforcing bars depending on the original male deformations of the reinforcing bars. The coupler comprising a pipe split along its longitudinal axis into two portions. The inner surface of each portion is grooved to form female grooves that exactly matching the reinforcing bar male deformations. The coupler is formed of one or two halves of the pipe portion assembled over the ends of the axially aligned reinforcing bars allowing for the bars male deformations to exactly enter into the pipe portion female grooves without any clearance or filling material to be added. Five techniques are applicable to tightly close the sleeve over the connected reinforcing bars ends. The outer surface of the pipe portions is processed to be used according to the technique of closing either one or two pipe portions over the reinforcing bars ends.