Tree knots are a type of wood grain pattern that can be found in trees. They are formed when the tree grows around an obstacle, such as a branch or a knot. The most common types of tree knots are knars, gnarls, and burls. Knars are small, round knots that form in the trunk of a tree. Gnarls are larger, more irregularly shaped knots that form in the branches of a tree. Burls are large, irregularly shaped knots that form on the outside of a tree's trunk. All three types of tree knots can add character and beauty to a tree.