Sash windows need a 3mm hole involving sash and body to operate with no friction stopping smooth travel. On the window that may be about painted, twisted, and warped the tolerance may be far more like 5mm in spots to allow passage of your sash at “sticky factors”. Brush seals https://caidenevkym.designi1.com/56736268/5-essential-elements-for-sash-window-draught-proofing