I use a rear sand bag for the butt stock on the bench. You squeeze it to adjust the alignment. Actually it is filled with rice which is a lot lighter than sand. In the field, a bag of styrofoam beads or air soft pellets works. I will also use a styrofoam bead seat cushion for a rifle rest. They are great to sit on in cold weather and have a double use. I have a couple of them in camo that clip to your belt.