A bed base for supporting a mattress, a mattress foundation or combination thereof or any other support structure has intersecting and interlocking side walls. Each side wall has an upper and lower web with configurations which engage and lock with the upper and lower webs of intersecting side walls at corners of the bed base. Cross braces are disclosed which extend transversely across the side walls, and which extend into the upper webs of parallel side walls. Legs on the cross braces may be co-located with the side walls and extend through the upper webs and down to the lower webs. The corners of the bed base may be reinforced with a corner piece which fits over the upper webs of the intersecting side walls, and covered by a corner guard which extends over portions of the side walls at the corners.