Twin / Full Slatless Flexing Hook-On Bed Rail Set with One 2-Leg Cross Support Adjustable width to fit Twin and Full size beds. The two legs on the center support ensure stability and can adjust from 8" to 18" Uses industry-standard hook-on connections for the headboard and footboard. Make sure the pins in your headboard and footboard are 2 inches apart before ordering. Approximate Dimensions: 76" Long (excluding hooks on end), 2" high with a 2" horizontal flange on which the foundation unit or mattress rests. Designed for use with a box spring under the mattress. No slats are needed with the center support system.