If the diagonals intersect at the center of the door, then one or both
are warped and replacement should solve the problem.
Otherwise secure a block in the center of one side of the door. The
height of the block depends on how big the door is. Run a cable
across the top of the block and down to the furthest opposing corners
of the door. Tighten the wire to bring the door back in shape.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.