An electromagnetic contactor that is designed for error-free assembly. The housing includes a contactor carrier interference that fixes the orientation between the housing and contact carrier. Orientation between the contact carrier and the armature is fixed by an offset elliptical joint. Pole shader interferences fix the orientation between the coil cover subassembly, the armature and the magnet. Shoulders located on two of four base legs fix the orientation between the housing and the base. The base includes a rail spring, spring catches, upper and lower catches that allow the contactor to be mounted on a DIN rail without using tools.