Clapboard is a long, thin board used on the outside of buildings, especially houses. Each board overlaps the one below it, like shingles on a roof, creating a weatherproof wall that sheds rain and snow. If you've seen a classic New England farmhouse or colonial home with horizontal wooden stripes running across its walls, you've seen clapboard siding.

The overlapping design is clever: water runs down the outer board and drips away before it can seep behind. This technique has protected houses for hundreds of years, from colonial times through today. Clapboard can be painted (white is traditional, but any color works) or left to weather naturally to a silvery gray.

The word is pronounced “CLAB-erd” or “CLAP-bord.” Originally, clapboards were split from logs rather than sawed, which made them slightly wedge-shaped and perfect for overlapping. While modern clapboard is usually cut by machine, builders still install it the same way: starting at the bottom of the wall and working up, each board covering the top edge of the one below it, creating that distinctive striped look that defines so much of traditional American architecture.