K'nex Winch
I made this winch a while ago but have not posted it until now. If you hold it down it can lift or pull heavy things.
This is the base and one of the walls that will hold the handle.
This is the axle which will hold the handle.
This is the handle.
This part makes sure that your load will not fall. To pull the string backwards push the metallic blue clip and the green connector down.
Put the top on and make sure that the rubber band is pulling the white rod down and you're done.