Abstract: A cover assembly, mountable without welds, includes multiple panels attachable together by structural support beams. The panels may be openable for access, or non-openable. The cover assembly may include gas-tight sealings between the panels and the support beams, and for scaling the cover assembly to a tank or other enclosure on which the cover assembly is mounted. The panels may be formed from a series of edge-to-edge planks and other plank-like components. Standard male-female connections allow parts to slide together to form panels. Interlock edge members are attached to plank ends of a panel thereby creating a rigid panel. Panels are connected to support beams using sliding latches. The inventory of available components enables various type panels to be configured and covers may be either flush or top mounted to a tank. All panels are removable. The cover assembly may be constructed in a rectangular, circular or other shapes.