Not what you were looking for? See Backyard Lever.
The Bookshelf Lever itself is a thin black cuboid that is shaped like a rod. Before the lever is pulled, it faces right. After it gets pulled, it faces to the left. Behind it is a stone/brick wall, framed with a dark gray material. (Probably also stone)
The main usage of this lever is to give the Player access to the Bookshelf Room and unlock the Slendrina's Mom Easter Egg. Go to Bedroom 2 and knock down the Painting. A lever will be behind it shown to the right. Pull it, and the bookshelf in Bedroom 2 will move to the right, revealing the Bookshelf Room.
- Before Update 1.5, there was nothing behind the Painting in Bedroom 2.
- Strangely enough, when the Player pulls the lever, it creates a noise but it doesn't alert Granny. However, knocking the Painting will.