The Maintenance Market can be found in the Town Hall of every village, represented by a wrench symbol. Here users can hire Construction Workers from other players to fix their structures for a price. If you need a House, Animal Stable or Herbalist Pot repaired that isn't in your inventory, simply make the Villager with the structure your Active Villager.
You'll still need to supply them with Wood, depending on how much is needed to repair the item.
Each village has a separate Maintenance Market. A villager cannot be hired by a user from a different village.