Knots

Knots occur where branches emerge from the trunk of a living tree. They are common in softwoods, with many species graded according to the size and number of knots in a board small, live knots are usually acceptable.  By contrast, knots in hardwoods such as European oak often attract a premium if they are relatively small because they enhance the appearance of the figuring.

Dead knots tend to work loose and fall out, so they should be avoided. It is necessary to avoid large knots when you cut the wood as it will weaken the board.