Switchboard

Switchboards are a kind of platform in Super Mario 3D Land and Super Mario 3D World. They are green and have two arrows, pointing left and right, each one on a pad. If the player steps on one of this pads, the arrow on the side they stand on will turn yellow, and the Switchboard will move over rails to the indicated direction.

Super Mario 3D Land
Switchboards first appear in Super Mario 3D Land in World 1-3, and appear in large numbers in World 1-4, Special 3-1 and Special 5-3. If there are small blocks at the end of the rails, the platform will simply bump and stop. Rails with no blocks on the end will cause the Switchboard to fall down.

Super Mario 3D World
Switchboards return in Super Mario 3D World, appearing in World 3-7, Switchboard Falls and, Cosmic Cannon Cluster where they are the main mode of transportation. This time, the border around the platforms is white instead of green.

Super Smash Bros. for Nintendo 3DS
Switchboards also appear in Super Smash Bros. for Nintendo 3DS in the final portion of the 3D Land stage, albeit without the arrows. They can be destroyed by Spike Pillars, which serve as stage hazards in the stage.

Mario Party 10
The Switchboard also appears in Mario Party 10 in the minigame Bullet Bill Bullies.

Trivia

 * A similarly functioning type of platform with four arrows and directions that it can move in appears in Hazy Maze Cave in Super Mario 64 and Super Mario 64 DS.
 * Another similar platform appears in New Super Mario Bros., more specifically, in World 7-2 from that game. It is also in the code of New Super Mario Bros. Wii.