XL Twin Size Hook on Bed Frame Rails with Cross Beam and Leg Xtra Long Twin Size. Adjustable center leg height. (Maximum leg rise is 10 inches from floor to top of cross bar) Please send us a message if you are unsure if it fits. Made in the USA. PLEASE MAKE SURE THIS BED FRAME FITS YOUR BED Hook on rails are typically used with wood type beds with a head and foot board arrangement. If you are trying to substitute those wooden rails that came with your bed, this set of hook on metal rails MIGHT NOT BE THE CORRECT ONES. Before ordering, please make sure your bed is compatible by verifying the measurements from the diagram below correspond to your bed. The hook-in slot between each rail must measure 40" in order to fit a Twin size foundation, which measures 39" Wide (Twin size)