Build the Simple Bed
A simple sturdy slatted bed is perfect for any child's room. This plan is designed so that anyone can build without special tools. If you can't locate 4x4s, try using two 2x4s glued together - but recalculate the dimensions - they will change very slightly.
Fits standards twin mattress
Materials and Tools
4 - 1x6 Boards 8' Length
4 - 1x4 Boards 8' Length
2 - 4x4 Posts 8' Length
2 - 2x4 Board 8' Length
3 - 2x2 Boards 8' Length
2 - 2x6 Boards 8' Length
120 grit sandpaper
A) 8 - 1x6 cut at 38 1/2" (these are the headers)
B) 6 - 1x4 cut at 30 1/2" long for the headboard (these are the rails) 6 - 1x4 cut at 20 1/2" long for the footboard (these are the rails)
C) 28 - 1x6 cut at 2 1/2" long (if these boards are splitting on you - depending on your type of wood - use 28 1x3s cut at 5 1/2" long) (these are the spacers)
D) 2 - 4x4 Posts cut at 41" (Headboard Posts) 2 - 4x4 Posts cut at 31" (Footboard Posts)
E) 2 - 2x4 cut at 50 1/2" (Top of the Headboard and Footboard)
FOR THE FRAME (Where the Mattress Goes)
F) 2 - 2x2 cut at 76 1/4" (Siderail boxspring holder)
G) 2 - 2x2 cut at 35 1/2" (Siderail boxspring holder)
H) 2 - 2x6 cut at 75" (Siderail)
Panels. Start by making the headboard and footboard panels. With a header board, A, alternate adding a spacer and a rail, nailing from the inside with 1 1/4" nails. The diagram shown below illustrates how to do this. Complete both the headboard and footboard. Use glue.
Now sandwich the remaining header boards as shown below, concealing the spacers. Use glue, and this time 2" nails. The diagram below illustrates these instructions.
Now let's add the posts. Predrill 1/2 way through the posts on the outside. Then use long screws (at least 4") to screw into the center panel where it is sandwiched between the header boards. Use two screws for the top header and two screws for the bottom header, for a total of 4 screws per post. Center the post on the panel. There should be a 5/8" space between the outside edge of the post and the header board on both sides.
Add the 2x4 (Board E)to the top of the headboard and footboard, as shown below. There will be a 2 1/2" overhang on either end.
Set the headboard and footboard aside. Build the below box out of the 2x2s. Notice how the shorter (G) 2x2s sit inside the longer (F) 2x2s. Use screws to screw through the outside of F into the end edge of G. Use two screws per end. Please note that the cutting list differs from the measurements shown below to accommodate a 75" long twin sized mattress, and the cutting list lengths are correct.
Add the siderails as shown below, leaving a 5/8" gap on either end. Screw through boards (F) into board (H). Doing this will hide your screw holes. Use 2 1/2" screws, screwing every foot all the way down the siderail.
Notice how the boxspring frame will attach to the headboard and footboard. Screw into the headboard, and screw at an angle into the four posts. You want to be prepared for little monkeys jumping on the bed!
Fill all holes with putty and sand and finish as desired. You can choose to assemble the bed (as in step 6) after the bed is finished and moved into the room. Just make sure you do a test fit first.
Links:  http://sewmuchado.blogspot.com/2010/06/wyatts-big-blue-bed.html