Blending hammers are best used for larger, softer high spots. Knockdowns are generally smaller tips, best suited for sharper damage. Metals that are harder (like steel) and sharp high spots are mostly repaired with a small, sharp knockdown. For high spots requiring a much stronger strike, we recommend using knockdown tips specially designed to prevent breaking or scratching the paint.
Tips are a very important PDR accessory but are often overlooked. Check here the best tips for your knockdown and blending hammer.