Hammer Pendulum

Swinging Hammers are a type of platform found in the New Super Mario Bros. sub-series.

New Super Mario Bros. Wii
Swinging Hammers first appear in New Super Mario Bros. Wii, where only two appear in the second half of World 8-6. They swing back-and-forth on a 180-degree arc, and can be used by the player as a solid platform.

New Super Mario Bros. U / New Super Luigi U / New Super Mario Bros. U Deluxe
Swinging Hammers return in New Super Mario Bros. U and New Super Luigi U, behaving exactly the same as in New Super Mario Bros. Wii. A new trait they possess is the ability to move on tracks. They appear in Hammerswing Caverns in the former and in Hammerswing Hangout in the latter.

Swinging Hammers reprise the aforementioned roles in New Super Mario Bros. U Deluxe.