I found this idea on this site and it really works. The target is made out of black insulated sheathing (Celotex). This is an old building material and may not be stocked at all building supply stores. Here is the procedure:

1st rip the sheets 12" wide and cut them to the length you want the height of the target to be. 24" , 32" , 48" etc.

The width of the target is determined by the number of 12" wide sheets you ripped. Each ripping will make the target 1/2" wide. For example, 64 rippings will yield a target approximately 32" wide.

Make 2 sides out of 2X12 about 12" longer than the rippings.

Connect the 2x12s with all-thread and sandwich the rippings in between the 2x12s.

I grooved out a 2x6 or whatever and set it on top of the bottom all-thread and on the bottom of the top all-thread to support the rippings better.

This is a great target to use. When you first start shooting it, loosen the nuts on the all-thread as needed, then as the target becomes worn, tighten them as necessary.