Knot holes form when branches die during growth and are overgrown by the trunk wood, or fall out after sawing. They are often considered quality defects in wood processing, as they affect the strength and workability of the material. In wood grading, knot holes are evaluated by size and frequency. In visible wood for interior finishing, however, knot holes can be deliberately retained as a decorative feature or filled with resin or epoxy. In structural timber construction, excessive knot holes in load-bearing components are critical and must be assessed according to standards. Rustic-style furniture, on the other hand, uses knot holes as a stylistic element.