The Kitchen Carpentry Cure

RAY: Here's the answer. He returned with something from the kitchen that solved the problem in an elegant fashion: the ice cube tray from the freezer. He simply placed a few strategic ice cubes on the sub-floor.

TOM: How many would you have used?

RAY: I would have used about eight.

TOM: I was only going to use four.

RAY: The ice cubes were placed on the sub-floor but the slate was placed above it. As the ice cubes melted, the slate lowered itself into the hole.

[ Car Talk Puzzler ]