Drawing is a form of visual art that makes use of any number of drawing instruments to mark a two-dimensional medium. Common instruments include graphite pencils, pen and ink, inked brushes, wax colour pencils, crayons, charcoal, chalk, pastels, various kinds of erasers, markers, styluse and various metals. The most common support for drawing is paper, although other materials, such as cardboard, plastic, leather, canvas and board can be used. Temporary drawings may be made on a blackboard or white board or almost anything. The medium has been a popular and fundamental means of public expression throughout human history. It is one of the simplest and most efficient means of communicating visual ideas. The relatively easy availability of basic drawing instruments makes drawing more universal than most other media.