substantially perpendicular to the plane defined by arm 6 and is inclined in an approximate 45 degree angle to the longitudinal axis 14 of longitudinal segment 7 the angle of inclination of plate 13 may be varied according to particular applications but will typically be within the range of 25 degrees to 65 degrees located within plate 13 is orifice 15 extending through orifice 15 is a linkage such as a partially threaded rod 16 as shown approximately 1 2 of rod 16 is threaded only the threaded portion of rod 16 passes through orifice 15 the position of rod 16 relative to plate 13 being adjustable by means of retaining nut 17 near the extreme end of the unthreaded portion of rod 16 is locking bar member 18 the locking bar 18 being permanently affixed to rod 16 such as by welding the pivot point of arm 6 is offset from the orifice 15 of plate 13 thereby providing a cam like action to draw member 8 toward bar 9 into clamping engagement with the door track the locking bar member 18 may be of any suitable shape and size sufficient to impede the travel of the door or rollers traveling within track 24 in the preferred embodiment locking bar 18 is a hollow metal rod approximately 1 2 inch in diameter and 3 inches in length bar.