Minecraft wiki entry for Elevators, associated text: Zipper elevators feature pairs of pistons stacked vertically. The stair version can be open on two opposite sides and is useful for giving views above ground. The no-stair version can be open only on one side. They have one major drawback, as multiplayer can cause a malfunction in the timing and cause the elevator to cease function. Also, adding a 1×2 piston on the top to push you onto a platform once you have reached the top to prevent the player from falling back down can be beneficial.