Bridge (instrument)
The bridge of an instrument in the violin family (violin, viola, cello and double bass) can be seen very clearly.  It is a piece of hardwood which is shaped like a bridge.  The top is like an arch in shape because the player needs to be able to play on one string at a time.  The feet of the bridge have to be shaped to fit on the front of the instrument (the “belly”) which is curved.  The bridge is not fixed to the instrument: it is only held up because of the tension (tightness) of the strings.  The soundpost, a small wooden column inside the body, is also held up by tension of the strings and the bridge.