This was my first attempt at making a baseplate bender. I use it to bend 1/4" could roll one at a time, if you want to bend several at a time or make baseplates out of flat stock you may want to build it a little heavier.
I made it with some scrap metal from work, so substitute with what you can find. The base is just 3" x 1"4" steel and I welded 3 "fins" on it for strength. The sides are just 1/8" angle iron and I welded a piece of 1/8" steel to it leaving about a 5/16" gap for the plate to slide up and down. The plate is just 2 pieces of 1/8" angle iron welded together and notched to fit into the track. The top is 3/16" with a piece of U-channel welded to it for strength. To make the bend I put welded a piece of 1/4" cold roll to the top and 2 pieces to the bottom plate (I am going to grind of the bottom 2 and weld 2 pieces of 1/4" flat stock on so that the baseplates bend straight).