What is used to create a seal against the knife edge on a water tight door or hatch?

A gasket is specifically designed for creating a tight seal between two surfaces, such as the knife edge on a watertight door or hatch. Its primary function is to prevent the passage of liquids or gases, which is critical in marine and industrial applications where watertight integrity is essential. Gaskets are typically made from materials that can compress and conform to the surfaces they're sealing against, ensuring an effective barrier.

In contrast, sealant is generally used for filling gaps and cracks but may not provide the same level of compression and sealing capability as a gasket. Adhesive tape is usually meant for bonding or holding items together rather than creating a seal, and caulking compound, while it can seal gaps, is also not as effective as a gasket for applications requiring a precise and reliable seal under pressure. Thus, a gasket is the preferred choice for ensuring that watertight doors and hatches function as intended.