Crankshafts

Crankshafts are obstacles first seen in Checkpoint 7 zone 2. They have a crank-like shaft of glass, and 3 metals. The obstacle is joined to two metal pieces, that help it spin.

They are re-used in zone 2 (and variants) of Endless Mode, as well as Local Multiplayer, and unused test stages. They first appeared in the Smash Hit Gameplay Trailer of a (fake) Checkpoint 4 (used as Checkpoint 3 (Version 0.8.0)), as well as the Credits (Version 0.9.0).

The crankshafts even have their own trailer (video link here, or here).