A less effective method is to install a rail on the wall, inside the door, that covers the gap. This still leaves a gap, but the rail greatly reduces the effect of wind.To seal the top of the door, install a flexible or hinged flap that spans the space between the wall and the upper urface of the door. The door must slide underneath this seal, so make sure that it does not jam or create excessive friction. In the case of a roll-up door, the seal must able to move over an wide range as the door winds and unwinds on the spool.