Sprocket

A sprocket is a special subzone of the battlefield where a Contraption is put when gets assembled.

Description
At the beginning of the game, a CRANK! counter will be put onto the third sprocket.

Whenever a Contraption is put onto the battlefield, it will always be put face up onto one of the three available sprockets.

At the beginning of your upkeep, if you control at least one Contraption, you move the CRANK! counter forward one sprocket (so, from 1 to 2, from 2 to 3, or from 3 to 1).