I was going to make a support for a new mattress when I spotted a sprung frame beside the road that was too big for the upcoming "kerbside cleanup".I figured the local authority would not mind my removing the item so I loaded it on and took home. I had to remove the spring assembly so went to grasslands where the staples/nails would not affect tyres. I only missed a couple of the staples/nails sending the others to scrap steel the next time I went. By doing this I saved my own precious lumber from screw holes and could burn this frame when finished using it.
I had originally intended using 4 by 2's covered with a framework of slats and constructing so that the 4 by 2's were a snug fit inside the trailer sides leaving a platform on which to place the mattress. I made one previously many years ago that concertinaed for storage but it still took up too much room. The other half of my equation suggested "why not just tie the base on the trailer?" Of course that could have done the job but I had 100+ Ks to drive and would have meant a lot of mucking around with tarps when the new mattress came in a heavy plastic waterproof bag.
My old 1972 7ft by 4ft box trailer was perfect for the job and my inconvenience collecting the mattress saved me about $50 after fuel.