A sketch is a rapidly executed free hand drawing that is not usually intended as finished work. A sketch may serve as a number of purposes. It might record something that the artist sees, it might record or develop an idea for later use, or it might be used as a quick way of graphically demonstrating an image, idea or principle. Sketches can be made in any drawing medium. The term is most often applied to graphic work such as Silverpoint , Graphite, pencil, charcoal, or pastel. It may also apply to drawings executed in pen &ink, digital input such as a digital pen, ballpoint pen, marker pen water colour and oil paint. The latter two are generally referred to as water colour sketches and oil sketches. A sculptor might model three dimensional sketches in clay, plasticine or wax.