What are holds and hatches on a ship?

The inner space of a ship between the limber boards of a double bottom and the decks is designed for carrying cargoes. We call this space a hold. Holds have different capacity. Big vessels have cargo holds divided into several separate compartments by watertight bulkheads.

Each dry-cargo vessel has four or five holds. The holds have bilges which serve to give way for flowing the water which may condensate on metal bulkheads or collect on wooden flooring. The water collected in the bilges is pumped out by a hold pump. To protect the bilges from corrosion they are covered with cement or special anticorrosion substance, besides they are protected by limber boards.

Holds

• Definition: Holds are the enclosed spaces or compartments within the hull of a ship where cargo is stored. These spaces are designed to maximize the amount of cargo a ship can carry and to protect the cargo from the elements and other potential damage.
• Function: Holds provide a secure and organized way to store various types of cargo, whether bulk goods like grains and coal or containerized cargo.
• Design: The design of holds can vary based on the type of ship. For example, bulk carriers have large, open holds for carrying unpackaged bulk cargo, while container ships have holds with cell guides to accommodate shipping containers.

Hatches

• Definition: Hatches are the openings on the deck of a ship that provide access to the holds below. These openings are covered by hatch covers, which can be removed or opened to allow cargo to be loaded into or unloaded from the holds.
• Function: Hatches serve as the entry and exit points for cargo. They must be designed to be watertight and secure to protect the holds from water ingress and ensure the safety and integrity of the cargo.
• Types: There are various types of hatch covers, including:
  • Side-rolling hatch covers: Common on bulk carriers, these covers roll to the side to open the hatch.
  • Pontoon hatch covers: Often found on container ships, these covers can be lifted off using cranes.
  • Lift-away hatch covers: Similar to pontoon covers but usually lighter and easier to handle manually or with smaller lifting equipment.

Holds are the storage spaces within a ship's hull, and hatches are the access points to these storage spaces, equipped with covers to protect the cargo.

The double bottom is covered with a removable wooden flooring. Cargo battens or "spar ceiling", as they are often called, comprises portable wooden battens fitted to the inner edges of the frames and so form a sheathing to the ship's side. "Spar ceiling" is made up of boards and arranged either horisontally, or vertically between frames. 

The purpose of this wooden sheathing is to prevent packages of cargo from damage by moisture which may collect on the side of the ship. The space so formed between the "spar ceiling" and the ship's side helps to provide a complete air space around the cargo and thereby improves ventillation. The "spar ceiling" should always be kept in a good state. 

Each hold has a hatchway. The hatchway is the rectangular opening in the ship's deck. The vertical plating around the hatchway is called hatchway coaming.