Metal Side Rails That Will Convert A Crib Into A Full Size BedĬlick here to browse our selection of metal side rails. You will need to purchase metal side rails that will convert a crib into a full size bed. If you no longer have the instructions you can contact a store that specializes in these types of bed frames. The most important thing you must determine before assembling this larger bed is to start by reading your crib directions. Great news changing it into a regular big boy or big girl bed is easy and its cheap. If you are a parent that purchased a bed that will grow with their child throughout the years chances are you purchased a convertible crib.