Abstract: An improved electronic circuit module retainer apparatus having interlocking, wedge-shaped components which are slotted and keyed together to allow tightening using a single screw which can be turned from the module insertion side of a module enclosure. A module retainer has a minimum of three interlocking parts which are held together by a tightening screw. A center body of the module retainer has holes for attaching it to a module or a module enclosure; it has a U-shaped channel with a square cross section and sloped ends. Each end body has a keying guide extending from a sloped end. A screw extends through a clearance hole in an end-body, then through the center body U-shaped channel and finally into a threaded hole in an opposite end body. When the screw is tightened, the end bodies slide along the sloped ends of the center body causing them to wedge the module against the module enclosure walls.