Abstract: 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.