A sectional door D having a plurality of panels (35), a first hinge leaf (44) formed on one edge of a panel and a second hinge leaf (42) formed on a second edge of the panel, wherein first and second hinge leaves on adjacent panels interrelate to form a hinge pivotally joining the panels, and a strengthening member (50) having a body portion (51) adapted to capture the hinge leaves and attachable to the panels near at least one of the first hinge leaf and the second hinge leaf.