Lead

Leads are items used to lead Passive Mobs.

Use
Using a lead on passive mobs will allow the player to move them. Multiple mobs can be held by leads, but each mob requires one lead. There are some passive mobs that can't be held: Bats and Villagers.

The player can attach the lead on any type of Fence, but not Cobblestone Wall.

Trivia

 * A lead can stretch a maximum of 10 blocks before breaking.