Repositioning backplate for an electrical outlet box

An electrical outlet box for use in existing buildings, wherein the building walls provide only limited access to electrical power cables in a stud space of the walls, where the box is inserted longitudinally into a conformably cut wallboard cavity with minimum clearance in the space, the electrical outlet box enabling work with said cables outside the space by securing a strain cable relief connector to a removable box component and reinstallation thereof in the box while preventing destruction to the wallboard surrounding the cavity, said electrical outlet box comprising a U-shaped frame with top, rear and bottom sections, identical left and right sidewall plates, each having interlocking tabs that project at essentially right angles from the plates for securing each sidewall plate to the frame, the rear section formed by a pair of elongate side members interconnecting said top and bottom sections and defining a rear opening through which electrical power cables can be drawn, each side member pair scored to facilitate removal of a side member by a twisting motion, an at least one hole through each side member to receive an at least one threaded fastener, and a repositioning backplate removably secured to the rear section to provide an enlarged cable port through which the cable can be passed upon temporary removal thereof, and an at least one fastener hole in the backplate corresponding to the at least one fastener hole of each side member to receive the at least one threaded fastener for re-securing the backplate to said rear section, whereby cable can be attached to the backplate and further electrical work completed remote from the box and the backplate remounted over the cable port and reinstalled in the box upon completion of the work.