Measure the height of a Pathfinder. Have him stand against the bottom of the tree you want to measure. Back off a convenient distance and hold a stick upright at arm's length. Sight so that the end of the stick seems to touch the Pathfinder's head. Put your thumb where his feet come. Holding your thumb tight against the stick, jump your thumb up to your buddy's head. Notice where the tip of the stick comes on the tree now, and holding the stick firmly, jump you thumb up again to this point. Find out how many times you can measure off your friend's height on the tree. Multiply this number by your friend's height and you have the height of the tree (or flagpole).