How to Fasten Interior Storm Window Into Opening

Measure the height of the window where you will be installing the interior storm window. Cut two pieces of 3/4-by-3/4-inch pine to this length. Install these pieces vertically along the inside face of the wall window frame, set back 2 inches from the interior edge, by nailing finishing nails through the strips of wood and into the window frame. Measure the horizontal distance between these two pieces on the top and bottom of the window frame and cut two more pieces of 3/4-inch-by-3/4-inch pine to this length. Nail these strips to the top and bottom of the window frame in line with the first two to create an inset frame within the main window frame. This gives you a bearing surface against which to press the interior storm window.

Place the interior storm window into the frame of the wall window so that the edges of the interior storm window are pressed against the interior face of the wall window.

Attach rotating latches to the finish trim of the window on the interior wall. Put a rotating latch onto the shaft of a screw and drive the screw into the face of the window's finish frame. Position the latch at the interior edge of the finish frame so that when it's turned horizontally it will prevent the interior storm window from falling out. Attach two latches to each side of the window frame, one 6 inches up from the bottom edge and the other 6 inches down from the top edge. After you have put the interior storm window in place, turn the rotating latches 90 degrees so they hold the interior storm window in place.