A proper backstop is essential for target shooting. It allows you to reuse the ammo and avoids ricochets - sounds good, doesn't it? Making a box backstop is simple:
The best readily available textile is three old t-shirts. They hold over 10.000 shots..I have the legs on an old pair of jeans, they also hold up well. Avoid soft towels and knitted pullovers.
This is the backstop of Bill Herriman. 3 t-shirts, a cardboard box and 2 office paper holders to attach the target.
Joseph Curven found a brilliant ready-to-use solution: Ikea sells this foldable fabric box. It is made to carry clothes with them, but we can put them to better use: Just put one or two old t-shirts in, add a string or clothespin to attach cans or paper targets and you got a professional-looking, lightweight, folding backstop.
I found these great drawings in a russian forum, and they show other simple and practical ideas. The sunchair-like one is very convienent, as the ammo is secured in the lower part, and you don't have to search the whole ground for spilled ammo. The large one between the trees is the stardart method for tournaments. I recomment to hang something heavy to the rug, so the wind cannot blow it around.