To replace the gasket on a double-paned window, press the liner mechanism to release the sash and remove the sash from the window frame. If fasteners such as screws or nails are present, remove the fasteners to release the window. Remove the screws from two sash corners, pull the sash away from the glass, remove the existing gasket and slide the new gasket into place. Reconnect the corners of the sash, and seal the corners of the sash with caulking.
To access the gasket after removing the window sash from the window frame, remove the screws from one top corner and one diagonally-located bottom corner of the window sash. When reinstalling the screws on the window sash corners, make sure the corners are evenly placed before tightening the screws.
When replacing gaskets on vertical siding windows, grasp the existing gasket at the top of the frame, and pull upward on the gasket to remove it. Repeat this process on all sides of the window, and clean the sash with a general-purpose cleaner.
Open the window to measure the length of the gasket, and cut the gasket to the appropriate length. Press the new gasket into place, and check the operation of the window to ensure the gasket is properly installed.