Free angle iron
Been doing this for years and just got done tearing one down, so I figured I pass this on as a FYI thing. Old bed frames are being thrown out every day. If you take them and drill out the approximately 20 rivets in them and remove the flanges for wheels and headboard, you end up with some nice 1 1/2 x 1 3/4 or 1 1/2 x 1 1/2 x 1/16th angle iron. Great for light fabrication or reinforcments. Takes about 45 minutes to strip. 1 kingsize frame with a center cross brace gives you 30 ft of good steel. And as I said, it's free.
It's all just nuts and bolts.