Queen hook in rails for Queen size bedding. Hook in rails require both a headboard and footboard to hook into and provide support. This is an excellent frame with a solid steel angle iron cross bar with 3 adjustable legs that gives the rigid center support needed. The rails are formed from one piece of 4 inch wide carbon steel with bedding sitting on a 2 inch wide horizontal flange. The flattened ends of the rails flex for safe, snug, firmer fit along the entire length of the box spring.