Rockshield Engineered Wood Products – Superior hardwood plywood products Rockshield Engineered Wood Products operates a plywood overlay mill in Cochrane, Ontario, the heart of renewable conifer and Aspen forests. The majority of panels are hardwood plywood to which Rockshi Rockshield Engineered Wood Products operates a plywood overlay mill in Cochrane, Ontario, the heart of renewable conifer and Aspen forests. The majority of panels are hardwood plywood to which Rockshield adds a hardwood veneer such as oak, cherry, maple, birch, etc., as an overlay to produce ready-to-use panels.