Abstract: A molded plastic, substantially planar, plate member which, when assembled, forms an open-topped electrical outlet box. The flat plastic plate member has end walls and side walls which are all foldable along living hinges relative to a bottom wall until further movement is prevented by raised projections to thereby form a three-dimensional box. Mounting sleeves are integrally formed in the end walls for receiving mounting nails. Flanges are also integrally formed in the end walls for receiving stamped Tinnerman-type nuts. Channels are integrally formed in the end walls and receive lateral edges of the side walls; slots in the channels receive tabs integrally formed on the lateral edges of the side walls. Additional tabs also integrally formed on the lateral edges of the side walls have U-shaped recesses therein for receiving the stem of the mounting nail with a snap-type action.