Natural wood defects: Coarse grain: If the tree grows rapidly, the annual rings are widened. It is known as coarse grain timber and possesses less strength. Burls: Burls are a deformed growth formed when a tree receives a shock or injury in its young age. Due to its injury, the tree’s growth is completely upset and irregular projections appear on the body of the timber. Bark pockets: Formed when a small piece of the bark protrudes into the lumber. This area is generally considered unsound. Bird pecks: Caused by birds, especially woodpeckers, which peck on trees mainly to cause panic to the insects living in or under the bark and in the wood of the tree.