A Timber bolt, also known as a Mushroom head bolt or Dome head bolt, is similar to a Carriage Bolt in appearance but with an oversized, heavy duty low profile head. Timber Bolts are typically used in marine and wood applications to protect timber structures from the elements. The underside of the oversize head of a timber bolt features rings that help prevent water from entering the hole and nubs or fins which prevent the bolt from turning. The timber bolt's oversize head eliminates the need for a washer on the bolt head side.