Does the mattress sit on top of, or inside, the frame? Tanner C. 06 June 2019 20:32 Updated Once assembled, your mattress will sit recessed inside the Endy Bed Frame. Related articles Does Endy sell a headboard? How do I build the Endy Bed Frame? What colours does the Endy Bed Frame come in? How do I ship the Endy Bed Frame back? Do you need tools to assemble or disassemble the Endy Bed Frame?