If you leave this page, the information you have entered will not be saved!
Are you sure you want to leave this page?
The gap at the bottom is fixed thing based on the overall length of the blinds. I most cases I have set these up from "longer" sets and then shorten to fit. if these are too short there is no way to make them longer.
Some blinds work better then others at blocking light when they are rotated closed. Not knowing the quality of blind it is that you have, there is little advice one can provide other then rotating them the other way so the angle is reverse what you would normally do when you close them.
It may be time for an upgrade to new
If they were made with vinyl or plastic, I'd recycle them long ago.
My windows are big and the sills are shallow, hard finding other options to work with. Unless I'm looking with my eyes closed Lol !