Begin your installation with the sill strip, which should fit as it comes from the package. To prepare the channel strips for installation, cut the top flange off at a downward angle to prevent snagging on the sash channel or sash cord. (Like bronze V strips, the flanged channel strips extend past the top of the meeting rail.) Then cut the bottom to conform to the angle of the sill, and to fit around the stool (the indoor sill). Note that the flange should be angle-cut high enough to saddle the bottom weatherstrip. Facing the window, install the left-hand piece of stripping using only three to five brads—one near the sill, one about midway up and one near the top. Again, avoid nailing into the sash-weight door. Next temporarily insert the sash, making sure the groove and flange mesh at the left and the sill. Then check to see that the window moves up down appropriately.
Remove the sash and prepare the right-hand weatherstrip in the same way. Insert the sash cord into the knot hole in the stile and install the left side of the sash into the left-side weatherstrip. Then insert sash cord in the right side, and weatherstrip into the groove of the right sash. Using a thin blade putty knife, gently push the sash and strip into the sash channel. Once the sash is seated, pull or push the right-hand weatherstrip down until it saddles over the sill strip. It is important to thoughtfully locate the brads on this piece so that you can remove the sash in the future by reversing the process. Insert the bottom brad near the sill. Insert the upper brad at the inside edge of the sash and weatherstrip edge so that it can be removed if necessary. Before installing the stops, make sure the windows glide up and down.