To get bolt lengths, I added up the thicknesses of the wood the bolt would need to span, and then experimentally determined a "magic number" to add to that to get the correct bolt length. This probably has to do with the bolt manufacturer as well as the thickness of nuts and washers used, etc. The bottom line is, for me, the bolts needed to be 0.75" longer than the total wood they needed to span. This yielded about 0.25" of bolt left over after the nut was put on, so a magic number of 0.5" would have worked too. In reality, I found myself more limited by the choices of available bolt lengths, and I had to settle for bolts longer than the optimal length. Bolts that had to have one end coming through at 45 degrees to the plane of the wood required more slop (experimentally determined to be 1.75"). However, there's an additional 1.75" in these lengths because the bolt is coming through at the center of the diagonal, or at the center of an imaginary 3.5" x 3.5" square. So these lengths have been written explicitly as 'plus 1.75" plus magic 1.75"'. I used half-inch bolts simply because I liked how they looked. Their strength is overkill. Whatever size you use, just make sure you use the same size drill bit. If you're like me and don't have a drill press, what I did was to mark the same hole on both sides of the wood, and drill halfway through on each side. I was usually able to get holes pretty close to perfect 90 degrees with this technique, although sometimes I'd have to enlarge the hole in one direction or another. No matter; it gets covered up by the washer. Measurements given here assume that a 2x4 is 1.5" x 3.5", and that a 4x4 is 3.5" by 3.5". This may not be universal, but it was true for the wood I got. The hypotenuse of a 3.5" board at 45 degrees is 3.5" * sqrt(2), or 4 15/16", or almost exactly 5". This figure is used in various places both as literally 5", and, halved, as 2.5". The legs have to be at least 8.5" long. They can be longer if desired. Take the desired height of the platform and subtract 5" (3.5" + 1.5"). Measurements here are given assuming the legs are exactly 8.5" long. Measurements given here are for a queen size mattress, which is 60" by 80". A king (aka eastern king) would be 76" by 80", and a california king would be 72" by 84". The boards, bolts, and holes to be drilled are all marked in greppable ways. To get a shopping list, grep for "need" (except in all caps. This instance isn't capitalized because, well, you get the idea.) After you've gotten all the boards and are measuring and drilling, grep for "board" (again in all caps) -- it will pick up both the "need board" and the "drill board" lines, allowing you to see first the boards that need drilling, and then what holes need to be drilled in them. The long pieces are 4x4s and need to be (2 * 1.5) inches longer than the length of the mattress. The mattress is 80" long so they are 83". NEED BOARD: two 4x4s, 83" DRILL BOARD: * 0.75" from each end, in the center (1.75" away from each edge) DRILL BOARD: * 11" from each end, but not in the center -- 0.75" away from DRILL BOARD: the outside edges. This requires deciding what is "outside". DRILL BOARD: * Turn over (a quarter turn) and drill 3.25" from each end, in DRILL BOARD: the center (1.75" away from each edge) NEED BOLT: four of 11.25" (10.5" plus magic 0.75") (short pieces) NEED BOLT: four of 10.5" (7" + 1.75" plus magic 1.75") (upright 2x4s & braces) NEED BOLT: four of 5.75" (5" plus magic 0.75") (attach to legs via short 2x4s) The 2x4s that go on top of the long pieces fit in between the short pieces and so need to be exactly 80" long (length of mattress). NEED BOARD: two 2x4s, 80" DRILL BOARD: * stand on narrow edge and drill at 9.5" from each end, in the DRILL BOARD: center (0.75" away from each edge) The short pieces are 2x4s and need to be (2 * 1.5) inches longer than the width of the mattress. The mattress is 60" wide so they are 63". NEED BOARD: four 2x4s, 63" DRILL BOARD: * stand on narrow edge and drill at 1.75" from each end, in the DRILL BOARD: center (0.75" away from each edge) The legs are 4x4s and are 8.5" long (or whatever you want). NEED BOARD: four 4x4s, 8.5" DRILL BOARD: * 1.75" from one end, in the center (1.75" away from each edge) DRILL BOARD: * Turn over (a quarter turn) and drill at 6" from the same end. DRILL BOARD: With 8.5" legs this will end up being 2.5" away from the other DRILL BOARD: end, but it's still best to measure as 6" from the first end. NEED BOLT: four of 5.75" (5" plus magic 0.75") (attach to long pieces via 2x4s) NEED BOLT: four of 7" (3.5" + 1.75" plus magic 1.75") (diagonal braces) The 2x4s that go behind the legs are 7" NEED BOARD: four 2x4s, 7" DRILL BOARD: * lay flat and drill at 1.75" from each end, in the center DRILL BOARD: (1.75" away from each edge) The 4x4 braces will be 8.5" * sqrt(2) at their longest, and 3.5" * sqrt(2) at their shortest. I found it helpful to draw as many lines to help me measure as I could before sawing. That way even if I didn't do the sawing perfectly I still had an accurate way of knowing where to drill. It also helped with the sawing since I had marked where the cut was supposed to go and I didn't have to rely so much on the miter box to tell me what 45 degrees is. NEED BOARD: four 4x4s, 12" SAW BOARD: with miter box, as shown in ASCII diagrams DRILL BOARD: as shown in ASCII diagrams. Two boards will be one way, the DRILL BOARD: other two boards will be another way. (Scale: four horizontal characters : one inch two vertical characters : one inch) 5" ******************** ** ** 5" ** ** ** ** Side view ** ** ** ** ************************************************ 12" ************************************************ * 3.5" <> 1.75" * Bottom view, as it should * * be for 2 out of the 4 * <> 3.5" * boards. Holes 3.5" from * * each end, one in the middle * * and one 0.75" from one edge ************************************************ ************************************************ * 1.75" * Bottom view, as it should * * be for the other 2 of the 4 * <> 3.5" * boards. Holes 3.5" from * * each end, one in middle, * 3.5" <> * one 0.75" from other edge ************************************************ --------------********************-------------- | / . . \ | | slanting . full thickness . slanting | Top view. Details below, | / down / . of 4x4 . \ down \ | examining each slanting side |foreshortened. .foreshortened| in a non-foreshortened view. | / . . \ | --------------********************-------------- ******************** * < - - 5" - - > * View of left slanting side (seen from above, but * * looking straight at the slanted surface), as it * * should be for 2 out of the 4 boards. Hole should * * come through in the center of the 5" (2.5" from * <> 2.5" * each side), and 0.75" from one edge. ******************** ******************** * <> 2.5" * View of left slanting side (seen from above, but * * looking straight at the slanted surface), as it * * should be for the other 2 of the 4 boards. Hole * * should come through in the center of the 5" (2.5" * < - - 5" - - > * from each side), and 0.75" from the other edge. ******************** ******************** View of right slanting side (seen from above, but * 1.75" * looking straight at the slanted surface), as it should * * be for all boards. Hole should come through in the exact * <> 2.5" * center -- 2.5" from each side in the 5" direction, and * * 1.75" from each side in the 3.5" direction. * < - - 5" - - > * ******************** 23 slats, each 59.75" (or 60" and be prepared to saw down the ones that end up not fitting). If only 22 fit and there's a gap just a little too small for one more slat, get a 2x2 of the same length and fill it in with that. NEED BOARD: 23 2x4s, 59.75" How it all fits together: 1. The long 4x4s go on top of the legs and get attached (loosely, just finger tight) with the seven-inch-long 2x4s and the 5.75" bolts. 2. Two of the short 2x4s go above the 4x4s, two below, and attach using the holes on the 4x4s nearest the ends, and the 11.25" bolts (finger tight). 3. The upright 2x4s go on top of the long 4x4s. Put the 10.5" bolts through but don't put nuts on them. 4. The braces go under the long 4x4s, attaching them to the legs. As you put each one in, you will need to lift up the 10.5" bolt from step 3, move the brace into position, and drop the bolt down again. Also put in the 7" bolts and finger tighten both them and the others. 5. First tighten the bolts on either side of the diagonal braces. Those need to come first, then you can tighten everything else.