Sheathing is a protective outer layer that covers and shields something underneath. The word comes from sheath, which is a close-fitting cover for a blade or sword.

In construction, sheathing refers to large boards or panels nailed to the outside of a building's frame, creating a solid surface before the final exterior (like siding or shingles) goes on. Think of it like putting cardboard around a model you're building before painting it. The sheathing helps protect the house from weather and adds strength to the walls and roof.

Sheathing also describes protective coverings on other things. Electrical wires have plastic sheathing wrapped around them to prevent shocks. Ships can have copper sheathing on their hulls to protect the wood from damage by ocean water and barnacles.

The key idea is protection through covering: sheathing acts as a barrier between something vulnerable and the forces that might damage it. When you see workers installing big sheets of plywood on a house frame, they're adding sheathing. When an electrician strips away the rubber coating on a wire, they're removing its sheathing.