Repair

Repair is one of the most useful and least understood skills that comes with the McMMO plugin. With it, you can repair damage to your weapons, tools, and armor. This is usually more cost-effective than using them until they break, and then crafting new items to replace them. Also, by using Repair, you can get by with only one sword, pickaxe, shovel, etc. in your inventory. Since you don't need a lot of backup equipment, you have more room for collecting materials in the wild.

How It Works
There are two things you need to carry to make Repair work: When your equipment has taken damage, you simply place the anvil on the ground, put the damaged item in your hand, and right-click the anvil with the damaged item. Some of your raw materials will be used up, and the health meter of the item will fill up.
 * An "anvil" (block of iron, crafted from nine iron ingots)
 * Raw materials of the appropriate type (typically iron ingots, but also wood, stone, gold, diamond)

NOTE: Any enchantments on the item may be lost during the repair process depending on your repair level.

When you are done, you can destroy the anvil with your pickaxe and put it back in your inventory. It will remain in iron block form, and not break down into its constituent iron ingots.

This skill must be leveled up through practice for quite a while before you will be able to repair diamond items. When you attain very high levels of Repair, you will be able to repair items without losing any enchantments. No more worrying about losing your Diamond Sword of Sharpness V!

For complete information, see the official McMMO wiki.