Field fortifications?

[valerio81]

I am planning to scratch-build field fortifications for my late XVII armies, the kind that a general would build on the front and flank of his army to secure his position from a menacing enemy.

If I am not wrong tree trunks would often be used. But how high these barriers would be? Would they also have some kind of turrets or mini-bastions..?

Would anyone have an iconographic reference I can peruse on the internet? Stamps,paintings, anyyhing would be useful.