Abstract: A longitudinally adjustable and lockable brace bar carries a pivoted foot piece at its lower end having a friction facing to prevent slippage while in contact with the floor. At its other end, the brace bar carries a pivoted yoke on a pivot axis which is parallel to the foot piece pivot axis. The bifurcated yoke engages beneath a door knob shank solidly with the yoke lying in a plane perpendicular to the door knob shank and perpendicular to the plane occupied by the foot piece while the brace bar is at an angle to the door enabling the device to resist entry through the door in an efficient and positive manner.