Abstract: A sliding plunger, normally about 1 cm. OD with a 0.5 cm tip distal end, controllably extends under spring force from a housing mounted to a wheelchair's frame transversely into a juxtaposed complimentary hole, preferably one of a circumferential array of approximately 24 such holes of racetrack shape, within an annular disk, typically 10 cm. OD with a 3.5 cm. ID center opening, that is mounted to the hub of the wheelchair's wheel at a position centered about the wheelchair's axle between the wheelchair's wheel and the wheelchair's frame. A cable extends from the sliding plunger's proximal end to a lever selectively activated by and occupant of the wheelchair to selectively permit that the sliding plunger should either (i) extend under spring force into a juxtaposed hole of the annular disk, locking the wheelchairs wheel against further rotation, or else (ii) withdraw easily from a hole, permitting wheel rotation.