the latch indicated generally by numeral 60 to lock the strut in the bracket while the upper slots 46 are shown as l shaped they will function satisfactorily if the slots are straight and disposed at an angle different from slots 48 the latter of which normally extend inwardly from the edges of the side walls at substantially right angles thereto the latch consists of a longitudinally moveable bolt 62 extending through holes in members 64 66 and 68 secured to side 40 and to flange 36 of base plate 32 in the embodiment illustrated in fig4 and 6 a spring 70 reacting between the underside of member 64 and a fixed collar 72 on rod 62 constantly urges the rod to its latched position which holds pin 52 in its seated position in slot 48 and secures the strut in body 30 of the bracket to insert the end 74 of pin 52 in the slot the rod which is provided with an overturned end 76 for use as a handle is lifted against the force of the spring sufficiently to permit end 74 of pin 52 to pass beneath the lower end of the rod and seat in slot 48 after pin 50 has been inserted in slot 46 as will be more fully explained hereinafter as shown in the drawings right and left bracket models are used in which the latch 60 in each model is on the inner side of the bracket thus requiring slightly different brackets depending upon the side on which.