Related Clues:

• Makes airtight
• Fills in the gaps?
• Makes watertight
• Makes watertight, in a way
• Seals around a bathtub
• Fills cracks in the decks with stoppers, say
• Fills cracks in decks with fillers or stoppers, say
• Bathroom seals
• Works with performing seals?
• Doesn't let anything fall through the cracks?