Me and my friends play on a rather large hill, most people call it a mountain...this is what we did...take rope, go around a few trees just on one side. then lay up a bunch of branches and stuff. after you have all the branches on there, take the rope and pull the rest of it around the other side so that the branches are inbetween the two ropes...next thing we did was take plants from the ground and stuck them in the branches so you couldnt see through the walls. after that we built stonewalls on the inside that were a few feet high(i live in alabama, lots of limestone that just breaks up into thin sheets of rock to just lay up on the branches, and one more thing, im not a hillbilly, i live in huntsville, huntsville has the most phd's per capita than any other city in the united states...ya we the rocket city)...then we just loaded more and more branches on the outside, making it really really thick...you can also put long branches or dead trees across in a diaginal formation between trees then stack sticks on it...you can also make a roof my layin branches acros the tops and stuff(just in case any1 trys to get smart with grenades), i think we might try to dig out some of the dirt on the bottom of it so its partially underground...our forts are top line...we have had our oldest stay up since beggining of april, and its still great...