Maybe OP means the rod is placed in the windows. I've done that.
I have day/night shades with valance on top on all my windows.
I took an expandable shower rod and put it "under" the top valance so you don't see it and I too bought room darkening drapes to hang on it.
1. At night no one can see in. They can with day/night shades. Yup I was surprised about that also.
2. It does keep the heat out from the hot sun in summer.
3. Keeps the cold out in winter time.
4. Makes a big difference on how efficient your ac and/or furnace will work.
4. you just push the drapes to the sides when not in use.