a releasable locking assembly for a door control cylinder is disclosed . the assembly fits over the rod of the door control cylinder and includes a locking flange member maintained in a confined space within a pair of concentric closed end cup members . the locking flange member engages the rod to hold the door control cylinder in an extended position by gently pushing on the outer cup member and disengages the locking flange member by further opening the door , allowing the cylinder rod to retract in a controlled manner .