Knots do not necessarily influence the stiffness of structural timber, this will depend on the size and location. Stiffness and elastic strength are more dependent upon the sound wood than upon localized defects. The breaking strength is very susceptible to defects. Sound knots do not weaken wood when subject to compression parallel to the grain.
Depending on the placement and size of a knot, what property of structural timber can be affected? (If the question is unanswerable, say "unanswerable")
stiffness