Assemble a regular steel bed frame by laying the two long rails parallel to each other, unfolding the top and bottom crossbars on each rail, and inserting each crossbar's pegs into the corresponding slots on the matching crossbar. After inserting the pegs into the slots, lock the frame into place before adding the box-spring and mattress.
Very large steel bed frames often incorporate a cross beam for added stability. This is a metal beam, usually with a single plastic or rubber foot, that fits into the frame. Install the cross beam by dropping it in roughly in the middle of the frame. Some cross beams simply float in the metal channels on each side of the frame, while others attach more securely using nuts and bolts.
Most steel bed frames have four slots near each corner for inserting feet or casters. Install feet by placing the plastic or rubber foot pieces over each slot before assembling the frame. Casters lock into the slots using a steel peg.
Some bed frames also have a plate at each corner. Each plate has numerous holes that are used for bolting the frame to a headboard and footboard.
Measure your mattress and box-spring before assembling the frame. Many frames have multiple sets of slots on each crossbar, allowing a range of different sizes. Use your measurements to choose the correct size setting for the bed frame.