Abstract: Mobile shoring rig to be used during excavation of trenches for laying underground pipe of varying diameter, includes a self-propelled carrier movable at ground level straddling the margins of the trench. A shoring frame supported within the carrier is vertically movable relative to the carrier for raising and lowering the frame into the trench being straddled by the carrier. The shoring frame includes a plurality of individual sheets or plates carried by a frame which are vertically movable with and relative to the frame on a plurality of longitudinally spaced guideways. The plates are of varying width to span one or more of the longitudinally spaced guideways and are slidable thereon for vertical movement together with and independently of the shoring frame.