A great project to help children to understand the application of ratchet and pawl, principle of variable speed as well as the pulley system. When constructing the high-rise building, those bulky bricks, if moving them up to the high floors by the constructon workers, they will be certarinly exhausted. But if moving them by the lift, it will be very easy. Now, do you know how the lift work? Let s using the building blocks to build up a lift and learning how it works.