A sturdy lightweight table support system offers advantages of self-squaring, sturdy design, a low unassembled volume combined with simple parts that enable easy assembly, a system that enables user specification of table size that will result in easily prepared components thus all but eliminating stocks of different sized components, and sturdy lockable height adjustments. The self-squaring is achieved with a corner bracket system that uses a corner bracket that is inset with respect to a cross member within which it is mounted so that bolted assembly will result in a large, even pressure about the butt end of the cross member against the post that is extremely resistive to angular displacement of the cross member with respect to the post in any direction.