Abstract: A door and window supplemental security device prevents unauthorized entry through a closed or partly open door or window by bracing the door or window against a floor or window casement. The device is rapidly and easily released in the event of a fire or other emergency. It may be folded in half for transport to hotels. The device includes an axially translatable rod actuated by a manually operated over center mechanism disposed at one end of the rod to lock the rod in an axially extended position. Brace means is disposed at the other end of the rod for frictionally engaging a fixed surface upon axially extension of the rod. The brace means includes a pivotally attached component which pivots upon extension to effect the frictional contact.