Elevators are special blocks that can allow you to quickly traverse your base vertically!
By placing two elevators with a gap between them, you can jump on an elevator to go up, and sneak on one to go down.
Variants change the appearance of an elevator, not the functionality.
You can switch an elevator's variant by Sneak-Clicking the floor with the elevator in your hand.
There are 3 variants: Up / Down, Up, and Down.
So for example, an Up / Down Elevator would have an Up / Down arrow on it's sides.