when i was little i used to make forts out of EVERYTHING.
things i made forts with -
umbrellas with towels
large sofa cushions
me and my brother also built two forts in the forest around my house. one had a tree as the central 'pole' and we placed large branches all around it to make a kind of wigwam type fort.
Another was one we built on the stream bank, with a large boulder as one wall. this one we went all out with and used planks of wood, it had a proper roof and all. we disguised it using moss and even had a secret treasure hiding place.
we found out after we moved house that a tramp lived in it for a while.
making forts was awesome.