A locking mechanism is contained within a carabiner's straight or bent gate. The locking mechanism incorporates a pivoting link that can be moved to abut against a transverse pin, thereby immobilizing the gate return spring, which prevents opening movement of the gate. The transverse pin is a material able to resist and distribute forces attempting to open the locked gate. The spring pin is notched to engage the transverse pin thereby simplifying assembly of the carabiner. A low profile protrusion is pushed in the direction of opening the gate to switch the mechanism to the unlocked position. Similarly, another low profile protrusion is pushed in the direction of closing the gate to switch the mechanism to the locked position. The locking and unlocking protrusions are located adjacent the gate hinge so that the gate can be conveniently unlocked, opened, closed and relocked with the fingers of one hand.