Abstract: An access cover assembly (10) has a cover member (12) and a frame member (14). The cover member has twelve vertical wall sections (36) with adjoining vertical edges (38) and twelve canted surfaces (40) with adjoining angled edges (46) depending downwardly from said vertical wall sections (36). The frame member has an upwardly facing frusto-conical section (80) and a number of substantially vertical edges (82) depending downwardly from an inner periphery (81) of said section (80), said inner periphery (81) being shaped such that when said angled edges (46) engage said inner periphery (81) when the cover is partially seated in the frame, the cover rotates towards a fully seated position in the frame member (14), whereupon the cover falls into and is locked within the frame member.