Not to be confused with the Repair Station. Durability Blocks can lose durability when being damaged by another player. For example, if you caught someone trying to mine through your walls and successfully fended them off, you will need to repair the damaged blocks, since they do not naturally regenerate durability. To repair blocks, you must have a Mallet, an item which can be crafted in the vanilla crafting table.

While holding the mallet in your main hand, hold the resource you want to use to repair the block with in your off-hand. Then, simply left-click on the target block to repair it. To check which resources a block wants to be repaired with, just click on it with the mallet while holding nothing in your off-hand. Note, when a block is first placed, it is on a cooldown and can't be repaired until it's building cooldown period expires, even if it is damaged and prevented from completely gaining full HP. When a block is damaged, a 30 second repair cooldown is placed on it. You can repair blocks anywhere, regardless if you have privilege over their region.