Midrails

Midrails, sometimes referred to as divider rails assist with the integrity of the panels and prevent them from sagging. If the height of your window is greater than 1800mm, Capture recommends adding a midrail. If more than 2032mm, you'll require two midrails. Midrails are also required if there are window winders. 

Midrails also allow the shutters to be divided into sections for light control, each section can be controlled separately.