Diy Twin Captains Bed Plans . The best way to create a twin captains bed is get the measurements off of the twin mattress you. Attach 3/4″ square dowel cleats to the 2x2s to support the mattress slats. Fantastic Full Size Captains Bed with Bookcase Headboard in 2020 Kid from www.pinterest.com Drill two 3/4 pocket holes into each end of the 1x6s. This bed was built for just $55 all said and done, making it a great budget project. Make sure the corners are square and add waterproof glue to the joints.