Abstract: An apparatus is disclosed for joining structural units. A structural unit, such as a precast concrete section of pipe, decking, bridge structure, building structure, or pavement, includes a plurality of spaced, longitudinally aligned tubular members. The ends of each structural unit are flush, and the ends of the tubular members are flush with the ends of the structural units. When two of such units are to be joined together, a guide member is inserted in one end of each of the first tubular members in the first structural unit, while an internally threaded insert member is inserted into a corresponding end of each tubular member in the second structural unit. The guide members and insert members have axial apertures with the aperture in the insert member being internally threaded. The two structural units are brought together so that each guide member on the first structural unit enters into the corresponding end of the tubular members containing the inserts in the second structural unit.