How do you fill gaps between roller blinds?

One common approach is to install pelmets or valances above the blinds. Pelmets or valances can be mounted on the wall or ceiling to conceal roller blind tube gaps and provide better thermal insulation and a professional finish.

Another option is to use cassette and side channels or tracks, which are attached to the window frames along the top and sides and help block out light and fill any top and side gaps.