leg structure for portable , height - adjustable gantries is disclosed having an upper , single vertical tubular post member telescopingly received within an open - ended sleeve formed by coupled aligned channel members of lower , break - apart sectional supporting framework . the channel members are supported and elevated by diagonal bracing members and struts giving a generally inverted - y shaped configuration to the leg so that it can straddle objects and permitting the free , unobstructed downward passage of the post through the lower opening of the sleeve . a locking bolt passes through aligned holes in the post and channels to selectively hold their relative positions , with hand - operated winch means aiding the movement of the post . post extension members are disclosed which can be added to the leg post while the gantry is assembled . the plate connection between the top of the post and a load - supporting i - beam is externally and internally braced by triangles and post weldment or casting insert elements , respectively . alternative embodiments show plate and tubular spacer channel coupling arrangements , and solid post - to - frame and non - breakdown frame leg configurations .