The mattress needs to be height adjustable. With this design there are 3 heights available. High, low and floor.
The frame is made of 3/4×3/4 ” 14 gauge steel tubing. It is sized to fit about 3/4″ inside of the wood frame.
The frame is supported at the corners, however the screw and nut locations would collide with the sides. So I used buried nuts welded into the end rail pieces prior to assembly. To do this the holes are drilled (#7) and tapped (1/4-20 ) 3/4″ from each end. A sacrificial bolt is inserted and a nut is placed on it finger tight. The nuts are then welded in place. I used a MIG welder. However the day was windy and my skills rusty after the long winter so they are not the prettiest of welds. (so feel free to pick on my weld quality)
I have often used this technique for buried fasteners when bolting through relatively thin stock like this or for beds where the nut plates are buried in the wood legs.
The holes for the webbing were then drilled in the sides. It is much easier to do this while the frame is still in pieces. I always make a list of the hole distances prior to marking and drilling. This is easy in a spreadsheet and minimizes the chances for an error half way through and the piece ending up looking like swiss cheese. I will use #8 x1/2″ hex head self tapping sheet metal screws. The holes are 9/64″ or #28 drill.
The frame was then welded up, welds ground flush, flap disk sanded (120 grit) primed and painted.
The webbing is 2″ light polypropylene webbing. I ordered a 150 foot roll and used most of it.
When securing the second end the triangle tip should hang over the side by about 1/2″. Now you start the screw through the webbing. Next you use a nut driver or impact driver and hex bit to lever the screw over after catching the tip in the hole. This adds just the right tension. Use hex head screws, I can’t imagine how frustrating this would be with just a straight screwdriver. The long straps are tighter than the sides and installed first as I did not want to bow in the sides
The frame is hung from these small pieces. They make the hole spacing forgiving and provide access to the screws that are otherwise hidden mostly by the frame. 1/4″ long spacers are placed between the straps and frame. These were made on the 3D printer, although you could also pay the price at the hardware store.
Now ready for delivery. Gap around the mattress is one finger thickness – just about perfect.