Knothole

Knothole refers to a hole in wood created when a knot—where a branch once connected to the trunk—falls or is cut away. In finished lumber, knotholes are voids in the wood grain that can affect appearance and strength. The term can also describe natural cavities in living trees resulting from branch loss or decay.

In lumber processing, knotholes interrupt the continuity of the wood fibers and can weaken boards. They may be exposed to moisture and insect attack. Finishes often cannot conceal deep knotholes, so they are filled with wood filler or epoxy, or boards with many knotholes are avoided for structural use.

Ecologically, knotholes in living trees create cavities that provide habitat for insects, birds, and other wildlife. They can be part of deadwood habitat networks in forests and urban trees, though large or unstable knotholes may indicate decay that compromises tree health.

The term knothole also appears in cultural language as a small opening used to observe from a hidden vantage point, such as peering through a fence knothole. In this sense, it denotes a tiny, private aperture rather than a defect in wood.