🔍 Key Concepts

• Watertight integrity and how doors maintain a tight seal • The function of knife edges and gaskets in making a watertight joint • How coatings, oils, grease, or paint can affect the sealing surfaces of rubber gaskets and metal edges

💭 Think About

• Think about what condition the metal edge and rubber gasket must be in so they can fully contact each other and seal against water pressure. • Consider whether adding any kind of coating (oil, grease, paint, etc.) would help or interfere with a tight, reliable seal over time. • Ask yourself what standard practice is on well-maintained ships when preparing watertight doors for inspection or pressure tests.

✅ Before You Answer

• Verify which choice best preserves full, clean contact between metal knife edge and gasket. • Check whether any listed coating could cause swelling, deterioration, or slipping of the gasket material. • Confirm which option aligns with good watertight door maintenance before a survey or flooding drill.