I use discarded steel tie plates found along rail road right of ways. The holes punched in them for the spikes, make easy attachment points for hanging. But in our use, we bend steel electric fence posts, [round rod about 3/8" in dia,], "S" bend them to support the plate a few inches off the ground. Works well from 5 yds to 100 yds on all pistol rounds up to and including 44 Magnum
They're roughly 8"x15" and vary in thickness from 1/2" to 3/4" in the middle portion which would support the steel rail when in actual use.
Center-fire rifle fire will damage them, although .22 LR from a rifle will not. The divets turned up by 2000 fps rounds of either jacketed or lead allot (They look like small scolloped edged craters) will cause some ricochets of splattered material, though nothing that's broken the skin [another reason if any were needed to wear eye protection].
Best regards, Rod