Fence

Fences are wall blocks that cannot normally be jumped over.

Obtaining
Wood fences are broken most quickly with an axe, but will drop when broken with any tool. Nether brick fences require a pickaxe to get it back, mining it with anything else will drop nothing.

Natural generation
Oak fences spawn naturally:
 * As the uprights for the supports in abandoned mine shafts, where they are plentiful.
 * In villages, where they appear in tables, lamp posts, and even enclosures on roofs or behind buildings.
 * In library rooms of strongholds as railings and chandeliers. In the latter case, there are many torches attached to them.
 * On the "patios" and in the front window of witch huts.

Nether brick fences can be found naturally in nether fortresses where they form window bars, balcony fencing, and gate-like structures.

In Pocket Edition, dark oak fences spawn as the supports in above-ground mineshafts.

Barrier
While fences appear to be a single block tall, and have a hitbox height of one block, their collision box (for entities) is 1.5 blocks tall, meaning most mobs cannot jump over them without the Jump Boost status effect. They are transparent to light and have visual gaps in the model.

A fence occupies the center space of blocks and automatically connects to any solid block that is placed next to it. Fences will connect to fences of the same type, and wood fences will connect to other wood fences, although wood fences will not connect to nether brick fences.

Since their hitbox is smaller than a single block, it will allow a player/mob in the block to breathe even when submerged.

Leads
Fences can be used to attach mobs with a lead.

Fuel
Wooden fences can be used as a fuel in furnaces, smelting 1.5 items per block.

Trivia

 * If a carpet is placed on top of a fence, a player can jump onto the carpet, while mobs will not (except rabbits).
 * Getting hit by someone else (or shooting yourself with a Punch enchanted bow while sprinting forwards) while in midair can cause the knockback to propel you over a fence you would not be able to jump over normally.
 * As mentioned in the 1.0 Release Changelog above. Prior to the release Fences could be placed under farmland to stop it being trampled. The removal of this bug was balanced out in a future version when simply stepping on crops was made to no longer trample them.