"Shooting at marks was a common diversion among the men, when their stock of ammunition would allow it; this, however, was far from being always the case. The present mode of shooting off hand was not then in practice. This mode was not considered as any trial of the value of a gun ; nor, indeed, as much of a test of the skill of a marksman. Their shooting was from a rest, and at as great a distance as the length and weight of the barrel of the gun would throw a ball on a horizontal level. Such was their regard to accuracy, in these sportive trials of their rifles, and of their own skill in the use of them, that they often put moss, or some other soft substance, on the log or stump from which they shot, for fear of having the bullet thrown from the mark, by the spring of the barrel. When the rifle was held to the side of a tree for a rest, it was pressed against it as lightly as possible, for the same reason."
Joseph Doddridge Notes on the settlement and Indian wars of the western parts of Virginia and Pennsylvania, from 1763 to 1783
So for Doddridge there was no need to carry anything to use as a rest such as the crossed sticks of the buffalo hunters on the Great Plains would use decades after the above was penned. The riflemen of his day, being in the woods, used natural objects to steady their shots. I don't take "offhand" shots in the woods for the same reason, and I move from tree to tree if moving, and halt at a good tree to break up my human outline and ALSO to give me something to help support the flintlock when I shoot.
LD