What do you do when the adjusting screw on a violin bow won't turn?

If the adjusting screw on a violin bow won't turn, first ensure that it's not stripped or damaged. Apply a small amount of lubricant, such as graphite or a specialized bow screw lubricant, to help ease movement. If it remains stuck, gently wiggle the screw while turning to free it. If all else fails, consult a professional luthier for assistance to avoid damaging the bow.