While a bunk bed with a twin-size bunk above a full-size bunk isn't as common as popular models with two twin bunks, they are just as easy to assemble. Different makes and models will have varying specifics, but most of the metal frames follow the same format. When assembling your bunk bed frame, following the specs provided by the manufacturer, even if they conflict with directions given here or elsewhere.
Clear the floor in the area where you want to install the bunk bed frame.
Set one end piece against the wall, approximately where the bed will be when completed. Make certain the piece is oriented correctly, with the wider bottom part facing the direction you want it to go.
Place the end piece in position opposite the first. This and the following steps will be much easier if you have an assistant.
Set the back bottom bunk rail in position, connecting the two end pieces at the bottom. In some models, all four bed rails will be identical. In others, you will need to use a specific rail.
Attach the back bottom bed rail to the end pieces, which vary from model to model. In general, you will attach it, using a nut-and-bolt arrangement. Hold the nut in place with your pliers and screw in the bolt, using a hex wrench or screwdriver as appropriate. Screw into place about three-quarters of the way in.
Set the front bottom bed rail in position. Attach as you did the first rail.
Position and attach the rear top and front top bed rails in similar fashion as the others.
Tighten down the attachments for all four rails until the frame is sturdy.
Lay the mattresses in place on the ridges of the bunk rails.