promotes such installation and use of a screen door and also insures that it is in properly sealed relation with the astragal and one of the side jambs 31 32 in each of its limit positions referring to fig1 the screen door 99 has its top and bottom mounted for sliding movement in conventional tracks not shown in the head jamb 30 and sill 33 a flashing strip 100 is mounted in each side edge of the screen door 99 by means such as the telescoping snap connection 101 with the flashing strip extending inwardly of the door opening as shown in fig1 when the screen door 99 is in its limit position at the left hand side of the frame and covering the opening for the left hand door 20 one flashing strip 100 will seal against the jamb 31 while at the same time the flashing strip 100 on its other side will seal against the arm portion 41 of the astragal similarly at its other limit position the flashing strips 100 will seal against the jamb 32 and the arm portion 42 of the astragal it will therefore now be seen that if desired for ventilation purposes the.