A Drophole is a bridge with a hole on it. The hole has been drilled to be big enough that any unaware marble can drop through it. Underneath the bridge, there is a sidepath which is longer and slower than the main path. Therefore, marbles must try to avoid this hole if they wish to keep their position. Sometimes, another obstacle like a pin or block can be placed just beyond the hole, which will prevent marbles from jumping over the hole so they can fall through the hole and be forced to take the slower sidepath.
