Abstract: Disclosed herein is a "drumhead" swimming pool cover assembly for a pool of predetermined size and shape having a circumscribing coping including a special male locking lip. The cover assembly includes a sheet of flat, flexible material having dimensions sufficient to allow the cover to drape the edges of the swimming pool coping, and a plurality of extruded plastic locking channels adapted to snap-on and lock to said locking lip along most of the pool periphery and to clamp said cover to said coping in a manner whereby the subsequent top loading of the cover increases the clamping or binding action of the channel and the lip with respect to the interposed cover portions. Advantageously, the coping to which the new drumhead cover is attached is of extruded aluminum construction, while the locking channels themselves are of extruded thermoplastic construction.