Anytime you use gear with your rope, there's the potential for damage. But with proper care and maintenance, you can minimize that risk. When it comes to a climbing rope ascender, as long as you use it correctly, it shouldn't damage your rope. Ascenders are designed to grip the rope tightly without damage so that you can safely ascend or rappel without fear of slipping. Of course, it's always a good idea to inspect your gear before each use and retire any pieces that show signs of wear or tear.