You an repair equipment and weapons if that equipment needs to be repaired (durability is less than maximum durability or, at the worst case, down to 0). Some equipment loses durability and thus will need to be repaired sooner or later.
Craft Repairing Edit
However, if the Armor Craftsman's skill is lower than the crafting level of the piece of armor to be repaired, some of that item's maximum durability will be permanently reduced. So, find someone with an Armor skill higher than the item that needs to be fixed to do the repair (maybe in your guild or nation), or take it to Reginn in Rome.