drag mechanism 60 causes the steel tape 32 to bunch up prior to being rolled in an interleaved fashion so that the steep tape and the sheet material can smoothly interleave fig5 and 6 show respectively the tape 32 and the blind material 24 in the extended and the retracted positions the rear wall of the cartridge assembly 22 has a lower lip portion which has attached thereto a snap on nylon rub bar 72 when the blind material 24 is fully extended it engages the outside surface of the rub bar 72 and provides a seal at the top end of the blind material so that the air is trapped between the glassed surface of the window and the blind material 24 overlying the window opening fig7 and 9 show mechanisms for centering the lower end of a roll of blind material 24 and the steel tapes with respect to the tracks 26 the lower end of the blind is clamped or locked in various positions along the tracks 26 by clamps also provided at the lower end of the roll a trim panel 80 shown in fig1 and 2 is fixed to the front lower edge of the roll of blind material 24 a spacer strip 82 is positioned between the trim panel 80 and the batten 50 the blind material 24 is near the batten and is sandwiched between two plates 110 111 as shown in fig8 a clamp mechanism 90 fixed to the trim panel 80 includes a hollow cylindrical sleeve 92 extending perpendicularly through an aperture in.