A. Scott Schiff responds: The coatings on power-driven nails are plastic polymers known as "thermoplastics." Their main purpose is lubrication: When the nail is driven, they melt from the heat of friction, making the nail slippery so it’s easier to drive. This allows the nail-gun to be built smaller and lighter.

When the coating cools, the plastic rehardens and creates a bond between the nail and the wood, so that the nail is harder to pull out.

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