Have you ever noticed how futile repairing in Minecraft can be? You combine two tools and get one with their combined durability. Now this is fine if you were running out of inventory space, however this is not useful if you want to keep a tool for long-term use, save your hard-earned enchantments, or be the town blacksmith. Now with Anvil, you can create an anvil block (if you have Spout; otherwise an iron block) and right-click with the tool or armour you want to repair.
To repair, you must have at least one of the base item in your inventory. For example, if I wanted to repair an iron pickaxe, I would need to have at least one iron ingot in my inventory. When I right-click the anvil (or iron) block, it removes the ingot from my inventory and repairs the pickaxe by 1/3 durability (because it requires 3 ingots to craft in the first place). This means a sword requires two to repair fully, shovels require one to repair fully, and so on.
