Minecraft wiki entry for Lead, associated text: With a mob on a lead held by the player, using the lead on any type of fence (or wall‌[BE only]) attaches the lead to it with a visible knot, tying the mob to it. To attach it to a wall on Bedrock Edition, the player must hold a lead in the main hand.[1] Multiple leads may be attached to one fence post. A mob tied to a fence tends to stay within 5 blocks of the fence post.