My window is missing a bit of plastic. I would like to replace it, but do not know what it is called to search for a replacement part.
Here is a picture showing a window that is missing the piece
Here is a picture showing a window that isn't missing the piece
The windows are manufactured by Window World.
Best Answer
The entire vertical window frame is called the “jamb”. The portion on the jamb that protrudes outward is called the “stop”.
It appears that this window manufacturer has pre-cut a notch (cutout) in the stop and frame in anticipation of installing a connector for screen, etc. to be applied later.
The piece that seems to be missing is the “cover plate” that covers this pre-cut cutout.