Knot Grade
Timber grading by number and size of knots.
Knot grade describes the classification of timber by its natural knot pattern. A-grade (also Select) is virtually knot-free with a calm, uniform appearance. Natural or Rustic grade shows lively knots and natural features such as medullary rays or small cracks. Country-house style allows larger knots and pronounced structures. The grading significantly affects both the appearance and the price of stair treads and should be chosen deliberately.