Minecraft wiki entry for Rube_Goldberg_machine, associated text: You probably had that terrible moment where you were building a sink bowl in a mob farm when all the water turned into source blocks. This source trick can be used as an RGM component. Make an almost-complete sink bowl, and then add a dispenser that adds water in the right way to turn the whole bit into a huge source. This allows the water to wash away a sand-supporting torch on the other side.