I'm planning on doing a game on the battle of Holowczyn soonish. One of the main features of that battle, apart from the insane opposed river crossing into a marsh by the Swedish, were the fortifications thrown up by the Russian infantry. So I decided I needed some of those and started building.
Fortifications in the early 18th Century (Holowczyn was fought in 1708) - and much of the 'Black Powder' era at that - probably consisted of gabions, lenghts of plashing and whatever woody bits were at hand. Well, that or what I happened to have at hand, which was:
The idea is that the further along the fortifications, the more hurried they become. So first there's gabions, then wood logs and branches stacked between stakes, then just logs stacked. The Russian army at Holowczyn was of course much more prepared and dug in than that, but sometimes historical reality has to bow to the rigors of time and bits availability :).