Place the structure between the mattress and the foot board and enjoy.
How to fill gap between mattress and bed frame.
Push the frame back against the headboard.
Secure the two longer pieces to the remaining short piece with 2 1 2 wood screws.
Then attach the right half to the left half using either pocket hole screws or angle brackets.
To make a cover for storage.
Place the hook into the next available groove.
Then use the area for under bed storage boxes and cover with a board and put a handle on it.
For the sturdiest fix simply screw one or more 2 inch thick.
Add the boxspring and mattress back to the frame and push them flush with the headboard.
Put the pillows on that area which now makes the bed longer.
Adjust the bed frame so that it is wider than the headboard by unhooking it at the middle and widening the frame.
Or get a board and put it at the bottom to stop the mattress from moving.