Bead fit blinds
Bead fit blinds are a good alternative if you like to have things displayed on your window sill as they fit into the window frame with no screws and no drilling. So, therefore the blinds take no space away from the window sill, as you open the window the blinds go with the window meaning there will be nothing flapping around. They are especially good for patio and bi-fold doors.
You have the option of a roller, pleated, cellular or Venetian blind with a variety of frame colours available. (Perfect fit or Intu)