Ok, I work with steel all day long, that doesn't mean I have the right stuff to make targets out of. I see lots of creative sources for steel. Not steel suitable for shooting mind you. See the pics in HPS' post. That is unsafe steel. If it has dimples or the face is cupped it will be returning bullet parts uprange. The target in medicgeek's post look great, the mounting method is a little ??? but to each his own. I USPSA or steel challenge we shoot flat steel all day at ranges down to 10 yards. A flat piece of steel hit dead on will drop most of a bullet very close to a target. No chance I would shoot at hps targets at 10 yards.
Made this duelling tree out of scrap iron. Especially fun w/two shooters; start w/2 paddles on each side and try to get them all on one side. Just bring Lots of ammo!
Side view showing hinge construction:
Looking down on hinges: