A knot is a particular type of imperfection in a piece of wood; it will affect the technical properties of the wood, usually reducing the local <answer>strength</answer> and increasing the tendency for splitting along the wood grain, but may be exploited for visual effect. In a longitudinally sawn plank, a knot will appear as a roughly circular "solid" (usually darker) piece of wood around which the grain of the rest of the wood "flows" (parts and rejoins). Within a knot, the direction of the wood (grain direction) is up to 90 degrees different from the grain direction of the regular wood.
What property of wood does a knot usually reduce in the wood around it?
strength