For some rifles, when benchresting them, you have to try to duplicate as closely as possible the way the forearm will be held when taking shots at game. A good example of this requirement is when zeroing or testing the Ruger No. 1. This is due to the two-piece stock/forend arrangement these rifles have. So when I shoot my No. 1's from a bench, I rest my left hand on the sandbag and grip the forend just like I do when hunting.

However, in the case of abolt action, most will shoot to about the same point of impact if you just use something relatively soft under the forend.A good sandbag is actually soft enough. Just don't use anything really hard-ahigh-powered rifle tends to shoot away from a hard rest, so the bullet will hit much higher than it would if fired offhand.....