Class C - the cheapest of plywood classes, which is used for use in construction when the appearance of the outer side of the plywood plays a secondary role. In class C, partially sound and unsound knots, holes from fallen knots up to a size not exceeding 40 mm, open cracks up to a width not exceeding 10 mm, edge defects up to a width not exceeding 5 mm are allowed. Healthy light and dark knots are allowed without restrictions on size and quantity. Lack of veneer up to 10 mm wide is allowed in the inner layers. Lack of veneer on the edges should not exceed 5 mm. Knots, cracks up to a size not exceeding 60 mm can be patched. False core, chemical discoloration, browning, stains are allowed. Repair with single and double veneer patches is also allowed in class C. Veneer overlays, indentations, sanding marks are also allowed in class C.