Cut all wood to dimensions shown on the "Things You'll Need" list. Use a compound miter saw and a table saw or circular saw. Specifically, cut two two inch by four inch boards to 84 inches long for the sides of the bed. Cut two two inch by four inch boards to 61 inches long for the head and foot of the bed. Cut the two inch by 12 inch board to 61 inches long for the support that goes at the head. Cut the one inch by six inch board to 64 inches long. Cut each plywood sheet to 42 inches by 64 inches. Cut the bed's feet from the two inch by six inch board. Cut eight pieces to 10 inches long each.
Smooth all pieces using a sander and 100 to 150 grit sandpaper. Use a slightly damp cloth to wipe away the dust.
Assemble the two inch by four inch boards to make the bed frame, which will hold the mattress. Place the boards that will make the sides of the bed on the outside of the ends of the head and foot boards. Visualize this by placing the fingertips of your right hand at a right angle to the palm of your left hand, making a T. Your left hand is on the outside of the end of your right hand. Your left hand represents the boards that go on the sides of the bed. They will cover the cut end of the side boards.
Pre-drill holes using a cordless drill and 1/4-inch bit. Whenever drilling into wood, try to place drill holes at least one half inch from the edges of the boards. To pre-drill holes for the lag bolts, start one half inch from the end of the board that's the side of the bed and drill all the way through the two-inch thick face, continuing to drill into the length of board perpendicular to it or the board that will form the foot of the bed. Drill another hole about one inch down from that, so the holes look like a colon ( : ) when you look at the end of the board. Replace the drill bit with the ratchet adapter and socket, using them to drive two lag bolts into the corner joint. Repeat drilling the holes and driving the bolts for each corner. You will have composes a rectangle of two inch by four inch boards when finished.
Position one of the pieces of plywood in the frame, flush with the top edge. Drive two-inch screws through the plywood into the two inch by four inch boards, spacing them every six inches around the frame. Place the second piece of plywood in the frame and attach it the same way.
Screw a one inch by four inch board to the plywood with 1.5 inch screws so it covers the line where the pieces of plywood meet and conceals the joint. You can also use wood filler to fill the seam, but it will require an extra day or two for the filler to dry and undergo sanding.
Turn the bed frame over with help from your assistants. Install the mending brackets. Space them evenly across the entire width of the bed and set them in place using 1/2-inch screws, which adds stability and joins the two pieces of plywood.
Attach four pieces of two inch by six inch board to the bottom of the two inch by 12 inch board at the head of the bed to make feet. Place them equally along the board. Mark their locations with the pencil and straight edge. Drive three-inch screws through the top of the two inch by 12 inch board and into the two inch by six inch pieces. Use two screws per board, for a total of eight screws here. Attach the remaining two inch by six inch sections with hinges to the bottom edge of the bed (see Tips). Space them evenly.
Stain, paint or otherwise finish the bed as desired. Allow to dry completely before continuing.
Move the head support--the two inch by 12 inch piece--into place. Use the large L-brackets to attach the support piece to the studs in the wall. Put three-inch screws into the studs through the holes in the L-brackets. Depending on the kind of bracket, this may take eight or twelve screws. Drive one-inch screws through the holes in the other half of the L-brackets and into the two inch by 12 inch board. Again, this is eight or twelve screws, depending on how many holes your brackets have. Be sure to leave the gate hinges open and attach them to the support.
Have helpers tilt the bed frame vertically and lift it onto the support. Attach the gate hinges to the bed frame with four 1/2-inch screws into the plywood and four two-inch screws into the two inch by four inch boards.
Place the barrel pins that will hold the bed in its upright position. Drill a hole in each bookshelf near the top, on the side of the bookshelf touching the bed. When the bed is folded up, the pins will fit into place and the bed will remain upright.
Have a helper hold the bed in the upright position and place the bookshelf units next to it. Anchor the units to the wall by driving one three-inch long wood screw through one side of each of the angle brackets and into the studs. Attach the brackets to the units. Use one 1/2-inch wood screw in each bracket to screw the brackets to the units. You'll use four of each screw here.
Install the drawers using 1/2-inch wood screws to attach the drawer slides to the inside of the bookshelf. Adjust shelf height if necessary. Add the mattress and bedding of your choice.