Abstract: A collapsible walker for elderly and disabled persons including first and second U-shape side frames which are pivotal relative to a front frame, enabling the walker to be collapsed substantially flat. At each corner between the front and side frames, a corner brace is provided in the form of a plastic sleeve which rides/slides on a horizontal rib in the side frame and a connecting rod which connects the sleeve to the front frame A detent in the sleeve snaps into catch slots in the horizontal rib to lock the walker in an open position. A pushbutton on the sleeve permits disengaging the detent from the catch slot.