Abstract: A metal foundation for a bed comprises a modular system of components easily assembled without conventional fasteners. The assembly includes parallel tubular side frame members of rectangular cross-section, each having two L-shaped pieces interlocked lengthwise in a sliding fit. Vertical stiffening ribs spaced apart along the inside and outside faces of the rectangular side members add rigidity. A pair of parallel tubular rectangular end frame members similar to the side members are at opposite ends of the foundation. Four L-shaped and tubular corner connectors of rectangular cross-section provide sockets to slidably receive the ends of the side and end frame members at the corners of the foundation. Longitudinal and lateral inverted U-shaped cross-slats slidably fit into corresponding slots in the inside faces of the side and end frame members.