My cl is trying to build a Rube Goldberg machine...And I need a little help about pulleys?

Our cl is divided into teams and each team has to make one part of the machine...My team is doing this thing where it's like a flying fox contraption and its transporting a marble from one end to another. We're using chairs as the things which are at the ends of the flying fox. Then our teacher said we should use a pulley instead to move the marble across from one side to the other? Like a spring loaded pulley? Does that exist? I...it just makes no sense to me, does anyone think that they can explain to me how a flying fox can come hand in hand with a pulley? Or something like that? Ok, can anyone tell me, how can a pulley system help in transporting something from one side to another? The "pulley" has to be horizontal, not vertical.