The gasket must be fitted on the outside of the door, between the faceplate of the handle and the door. You can find more information on the mounting instructions, which will be available through your handle's product page. See example below:

https://www.se.com/uk/en/product/KCF1PZ/tesys-vario-mini-vario-front-and-red-rotary-handle-1-to-3-padlocking/

Released for: Schneider Electric UK