The bow should always be straight. The bow should feel comfortable in your hand. Gradually your bow hair does wear out. The hank of selected hairs is then bound together and held into each end of the bow with wedges to form an even ribbon of hair. This is a very skilled job so a good re-hair is not particularly cheap, but the results are worth it. Bad re-hairs can damage your bow or come undone in the middle of a performance. Allow time for your re-hair to play in. Fresh bow hair won’t hold rosin properly at first and can sound very rough. Apply a balanced loading of rosin and prepare to spend an hour playing it in, though fifteen minutes of aggressive open string chords is usually enough to clear the worst of the roughness from a new re-hair. Make sure your bow is comfortable to hold. Many cellists prefer a short re-hair which leaves the hair only just slack when the adjuster is fully unwound. A short re-hair ensures that the frog stays close to the thumb grip when the bow is tightened and also means that the balance point of the stick stays close to the player’s hand, avoiding the bow feeling tip-heavy when playing. Another advantage of a short re-hair is that it allows for the tendency of hair on a cello bow to stretch in use. Some cellists get a leather flap fitted to the thumb grip to protect their thumb from the sharp edge of the frog. Others thread a pierced rubber thimble or section of rubber tubing over the stick to increase the size and comfort of the stick and to cushion the thumb. All such techniques prevent damage to the bow stick from the thumb nail. Clean your bow stick with a dry duster to remove rosin dust which will otherwise build up on your bow. The bow should be routinely cleaned when it is re-haired. Avoid touching the bow hair with your hands as grease from your fingers will attract dirt and stop the rosin from sticking to the bow hair.