I have a similar system of sliding window that uses a U-shaped stainless steel
rail and plastic strips attached to "fuzz" so that the window does not slide freely on its own, but does move when you push it. The frame is held in place with bedding compound. Someone before me had put screws through the stainless which caused water
to get into the wood which caused dry rot
. It used to be plastic similar to Plexiglass which scratched easily but is now laminated glass. I had a local glass shop cut the glass for me.
I use a bottle washer and some glass cleaner to get in there to clean it.