What Makes a Knot in a Piece of Wood?
A knot in a piece of wood is simply a lump, or growth, formed at the point where a branch grew out of the tree trunk. When the tree is cut down and sawed into boards, the “root” of the branch shows as a roundish place in the board. As the board dries and shrinks, the knot may fall out.
We often see knotholes in board fences where knots have fallen out. Knots are imperfections that cause living wood grain to grow around them. Knots are common in some woods. Knotty pine, for example, is full of knots. This wood is often used to make decorative walls and ceilings. The wood within a knot is very hard, as carpenters well know.
It makes perfect sense when you think about it. If wood knots are produced by the death of a branch, how could they contribute to the strength of the remaining wood that lives?
The human equivalent would be a gall stone, an imperfection which painfully weakens the performance of a gall bladder. Remove the gall stone, and the bladder recovers. Dead branches leave wood knots behind. Such imperfection is just part of life as we know it.