Lever

A Lever is one of the four switches currently in the game. Levers - like the Stone Button, Pressure Plate, and Redstone Torch - can be connected with Redstone (Wire) to be operated far away from the target block. You can place levers on any non-transparent block.

Crafting
Levers are made from a stick and a piece of cobblestone, and can be placed on both walls and floors.

Power
Levers differ from buttons in that the charge they provide is stable - once clicked a lever will remain on or off until clicked again. Clicking a lever also causes a visual change as the shaft of the device moves from one side to the other. Their stable nature makes levers well suited to controlling devices that need to remain in one of two states for an indefinite period, such as minecart tracks or locking mechanisms in advanced circuits.

When placed on the side of blocks, up is OFF and down is ON. On the top (or since 12w24a, bottom) of blocks, ON is south or west, OFF is north or east.

History
The lever was implemented along with the button and pressure plates in Alpha 1.0.1. As of 12w24a, levers can be placed upside down.

Trivia

 * The lever, along with wall mounted Torches, flowing Lava and Water, sloped rails, Tripwire Hooks, and Snow golem's arms, are the only surfaces in Minecraft that are not either parallel or perpendicular to the ground.
 * The rotation of levers placed on the top of blocks is decided randomly and not influenced by the rotation of the player.
 * Anything powered by a single Redstone Torch, such as a Powered Rail block, can be replaced with a Lever. This is useful if you are low on Redstone.
 * Levers cannot be placed on snow or ice.

Hebel Lever/es Levier Lever/ko Schakelaar Dźwignia Рычаг 拉杆