If you are talking about the front door glass of a beetle then -
- You will need to wind the glass down fully.
- undo the two bolts for the actual window clamp which hold it to the winder regulator. That is the bit that goes up and down.
- drop the glass down that little bit further.
- take out the inner scraper by carefully levering the scraper and popping the clips
- lower the top section of the bailey channel, near where the quarter glass top is. Bailey channel is the U shaped felt the glass runs in.
- undo the screws and bolt for the triangle quarter glass vent window.
- pivot the quarter glass assenbly back at the top and draw out upwards, being careful not to scratch paint or damage outer scraper.
- lift glass out and pivot so that lower channel comes out where quarter glass was.
- it is at this point you may replace the outer scraper if you wish.
If the lower clamp is still holding good, then I do not recommend you remove it. There is a risk of breaking glass, or putting it back in the wrong spot.
assembly is reverse.
Hope this helps.