2) Trees are of course a nice obstacle, unless you are driving a tank. The most inportant thing about the use of treelines is that they must be trimmed up from the ground...a great hiding place for recon units and sniping positions...Most are trimmed up about 4 feet up from the ground level, BUT I have discovered that going up as far as 6 feet up, allows for a clear and unobstructed view, even in heavy winter snows, of ANY intruders and movements. I used many trees in lieu of fence posts, that saved me considerable costs and time to drive and anchor posts. U shaped staples and several strands of double barbed wire, make for a helluva nice fence line. Want to keep peole off the trees and from climbing up them? Wrap barbed wire around those puppies!