Corner Unit for the Twin Storage Bed

Build the two bookcase boxes from 1x12s. Screws (2") are stronger, but nails and glue are easier to hide and fine here since these get boxed in. Keep them square.

Fasten the 1/4" backs on with 1-1/4" nails and glue, fastening to the back shelf too. Finish the bookcases now — paint or stain them at this stage while they're easy to reach.

Fasten the 45°-beveled cleats to the insides of the bookcases with 1-1/4" nails and glue. Crucially, the cleats are NOT on the same side of both cases — line the bookcases up the way they'll sit in the corner first, so the beveled ends will meet.

Paint or finish the MDF face and the top piece independently — they go on during room assembly. Clip the angled corner off the 40-1/2" top per the layout so it fits the nook diagonal.

In the room, screw the face to the meeting cleats with 1-1/4" screws, add the 2x2 back supports and back leg, and fasten the top to the tops of both bookcases and the back supports. Level it and confirm it ties the two beds together cleanly.