To optimize blackout, we recommend installing your roller blind outside the window frame, as the fabric will be approximately 20 mm inside the bracket, which in some cases can create unavoidable light gaps. We also recommend choosing an under-rolled roller blind to optimize blackout. My Window asks you as a customer to be aware that even when selecting a roller blind with fabric classified as blackout, light gaps may occur. Why do these occur? Possible reasons can include the placement of window handles, the distance of the fabric or material from the window, and the prevailing installation conditions. Therefore, My Window does not guarantee that products with blackout fabric or material are 100% blackout.