scaffold planking must be made with _______-grade lumber.

Scaffold planking must be made with scaffold-grade lumber. This scaffold- grade lumber meets specific strength and quality criteria that are more stringent than construction-grade lumber, including higher standards for knots, grain slope, and absence of pith or juvenile wood. Construction-grade lumber is not suitable as it has only about two-thirds the strength capacity of scaffold-grade lumber and may not safely withstand the forces applied in scaffolding applications. Scaffold-grade lumber is typically marked with a grade stamp from a recognized grading association or inspection agency to certify its suitability for scaffolding use.