Choose a tree limb near the front door of the tree house, but above the top of the door. Cut a 12-inch piece of clothesline and tie it around the branch near the house, using a secure series of knots. Leave one long end of the clothesline hanging down.
Tie the top loop of the pulley to the loose end of the clothesline. Use multiple knots to create one large chunk of knotted line, so the pulley won't come loose from the line.
Measure the distance from the pulley to the ground. Multiply this distance by three, and cut that length of clothesline.
Punch one hole in each side of a plastic storage bin with a screwdriver. Place each hole directly below the rim of the bin, centered on the side. Make the holes larger with a knife or scissors, if needed. Make sure the holes are large enough for the clothesline to thread through.
Cut four pieces of clothesline that each measure 2 feet long. Thread one end of each piece of clothesline through a hole and secure it with a large overhand knot. Pull up all four loose ends and tie them into one overhand knot directly above the center of the bin. Cut off any excess clothesline that protrudes from the top of the central knot.
Tie one end of the long length of line to the knot on top of the bin. Thread the other end of the line through the pulley and drop it back toward the ground.
Hammer a brightly colored tent stake into the ground near the base of the tree. Wrap the loose end of the clothesline around the base of the tree. Measure the line at this point to see how much more line you need to create a loop that reaches the tent stake. Cut off the line if needed, make a loop at the end of the remaining line, and slip the loop over the stake.