BCY Bearpaw Bow String Serving Tool. The Bearpaw serving tool has proven to be one of the best available. BCY hit a home run with this mid price range, German designed server. It's rugged design and heavier weight makes it the perfect choice whether you are a DIY bow string builder or run a professional bowstring business. The stainless steel rollers allow the serving to be guided smoothly. The slotted head allows the serving to be threaded extremely fast. With an adjustable tension knob you can be precise in how tight the servings are applied.