Back away from a flagpole or tree that you want to measure. Hold a stick upright at arm's length. Sight over the stick so that its tip appears to touch the top of the pole and your thumb is at its base. Swing the stick 90 degrees to a horizontal position as if the flagpole were falling. Keep your thumb at the base of the pole, and notice where the tip of the stick seems to touch the ground. Pace the distance from that point to the base of the flagpole to get its height.