The attached photos show one of the bracket assemblies I made to attach stirrups to boards that can be slipped between my box springs and mattress.
I used (2) thumb screws, but I will later replace them with hitch pins that have spring-loaded detent balls (in order to keep the hitch pins from falling out).
The bracket assembly is not finished, because corners have to be rounded on the aluminum angle pieces in order not to get cut.
Don't use 1/16" X 1" X 1" X 3" aluminum angle as I did. I suggest that you use 1/8" X 1" X 1" X 3" steel angle instead, because that thin of an aluminum angle may be too weak for forces involved (this remains to be seen).
What you see here is not complete yet, so don't be concerned if you see something that may cause you to want to ask me why I did something the way that I did.
Stay tuned for more photos of my progress.