Much of the strength of the instrument comes from its shape; the wood itself is quite thin. Furthermore, the strings put a lot of force on the instrument. Simply knocking over the bridge may cause seams to open. A slight blow to the right spot can be transmitted by the soundpost to cause a soundpost crack on the top or back, especially if the soundpost is too tight. Dropping the instrument may break the neck off. Even if no damage is immediately visible, a blow can shatter glue, causing a nearly untraceable buzz, and leading to open seams or cracks later.