An extensible bar comprises a bar and a sleeve that slide over each other and are kept together by a pin. The extensible bar includes a locking system made up of a latch connected by a wire spring to the sleeve, the latch preventing sliding movement between the sleeve and the bar when the latch is positioned within respective recesses formed in the bar and in the sleeve when the recesses are aligned. The wire spring urges the latch into the recesses. Unlocking of the assembly entails pulling the latch out of the recesses by grasping and pulling a handle attached to the latch. The locking system can be blocked by turning the latch about the wire spring into an orientation that prevents the latch from entering the recesses. The locking, unlocking, and blocking functions are performed by an assembly of only three parts; the latch, the wire spring, and the handle.