Abstract: A rebar coupler having a casing with two opposite ends disposed along a central longitudinal axis. Each opposite end includes a frustum-shaped internal wall tapering along the axis from an inward to an outward position, as well as an assembly of a plurality of locking jaws, arrayed around the axis and engaging the internal wall, at least a portion of a spring, aligned with the axis and engaging the locking jaws, and a spacer, initially positioned within and engaging the locking jaws to separate the locking jaws and bias the assembly towards the inward position. The spacer is ejectable from the locking jaws through a center of the spring by insertion of a rebar end through the outward position and past the initial position of the spacer, whereupon the spring biases the locking jaws toward the outward position and into full engagement with the rebar end.