Tailpiece
The tailpiece may be wood, metal, carbon fibre, or plastic, and anchors the strings to the lower bout of the violin by means of the tailgut, nowadays most often a loop of stout nylon monofilament that rides over the saddle (a block of ebony set into the edge of the top) and goes around the endpin. The endpin fits into a tapered hole in the bottom block. Most often the material of the endpin is chosen to match the other fittings, for example, ebony, rosewood or boxwood.
The picture on the right shows how a boxwood tailpiece is hand carved with a beautiful figure by a carver in India.
Very often the E string will have a fine tuning lever worked by a small screw turned by the fingers. Fine tuners may also be applied to the other strings, and are sometimes built in to the tailpiece. Fine tuners are usually used with solid metal or composite strings that may be difficult to tune with pegs alone; they are not used with gut strings, which have greater flexibility and don't respond adequately to the very small changes in tension of fine tuners. Some violinists, particularly beginners or those who favor metal strings, use fine tuners on all four strings. Using a single fine tuner on the E string, or using built-in-tuners, limits the extent to which the tuners' added mass affects the sound of the instrument.
Read more about this topic: Violin Construction And Mechanics