Page #5 DIY BED Instruction
Now with all four sides bolted together (not with nuts), the hardest part is over. After all is done and hooked up, we now move onto establishing and securing support for the mattress, you, and…
Installing the center support beam for the platform bed, begin by marking the very center of both sides (head/foot side) of this bed. Also mark for our 1/2″ inch gap to find where the 2×4 support stud beam should go.
< marking the center 
< marking the 1/2″ gap
Then trace lines around where you want to install the 2×4 Stud support bracket and disassemble your platform bed so you can drill on screws better and hammer in the built in notch on the support bracket.
Do the same for the opposite side, then measure the length from that stud support bracket to the other support bracket on the other side and cut a 2×4 stud of that length. That measurement should be within an inch or two of the length of your mattress size.
With the platform disassembled, the next thing to do is to install our support rail on the other long sides of this bed. This support rail, 1/2″ inches from the top, will hold 3/8 plywood or long 1/2″ inch strips of wood like IKEA does to support their bed. Go to their stores or order at IKEA.com
As pictured above, the unattached support rail is long and thin (scrap wood 1/2″ thick) cut into two 4′ feet strips and pre-drilled (with a small drill bit) in four places ready for screws. I apply glue to one side of the support rail and screw onto the inside of the board with my 1/2″ inch gap in mind. Pre-drill your rail and use 1 1/2″ inches screws.
Note: If you select a wood plank strip support system instead of plywood, make your support rail the entire length of the side boards. You don’t want gaps with a wood plank strip support system, planks will fall out.
<glue, then drill screws on
Now, how about wheels / castors? They will be great with my wood floors and is gentle on most surfaces and are lockable. I installed two opposing lockable castors and two opposing regular castors to save money instead. To skip castors, go to Step 8 of this DIY.
It is fairly easy to install castors, just flip over the platform frame and pre-drill your four holes where the castor is centered then screw in small screws around 1″ inch long.