Insert pencils or dowels in two large spools to create pulley wheels, ensuring that the spools can turn freely. Another option is purchasing pulley wheels from the hardware store.
Tie the ends of a piece of string, yarn or rope together to form a big loop. Place the loop around the spools or wheels.
Attach the spools or wheels to fixed objects far enough apart to give the line a light tension, or ask two friends to hold the spools at the same distance.
Write a secret message on a piece of paper and attach it to the line at one end with a paperclip. Turn the wheels or spools with your hands, or ask the person on the other end to pull on the line to move the string through the pulleys and deliver the message.
Screw one pulley wheel to the lower edge of a treehouse just outside the door. Screw a large eye hook into the inside floor to one side of the door.
Thread a piece of rope through the eye hook and knot the end several times so it will not pull through the eye. Thread the other end of the rope through the top of the wheel and let it dangle to the ground.
Tie the loose end of the rope around a bucket handle. Load the bucket with snacks or other materials and pull the loose end inside the treehouse to bring your load on board.