These targets do not stop most bullets, you will still need a backstop to catch your bullets.These targets are not invincible, and will periodically need to be replaced or repaired, but since they're made from recycled materials it should be cheap or free to fix.
This is the part where I warn you to be careful and always observe proper safety procedures. No one likes getting shot(at least not anyone I know) and hospital bills/jail time can really ruin your day. Be careful because if you get hurt, it's not my fault, and depending on how serious the injury is, I may laugh at you.
Step 1: Supplies
7x Wire frame storage shelf panels
Lots of light gauge steel wire(probably over ten feet, it was holding a roll of chicken wire together) This could be replaced with zip ties though assuming you used some decent zip ties.
2+x cuts of gardening tie(mine are just over a foot long, and not the same size)
3x Brass hooks per cut of gardening tie(again, feel free to make substitutions)
1X Roll of duct tape!(if you have lots of wood around you could skip this, but I'd do it anyway)
I didn't include a list of tools because each build is a little different. You know what tools you need.