Drawing is a 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 color pencils, crayons, charcoals, chalk, pastels, markers, stylus, or various metals like silverpoint. An artist who practices or works in drawing may be referred to as a draftsman or draughtsman. A small amount of material is released onto the two dimensional medium which leaves a visible mark—the process is similar to that of painting. The most common support for drawing is paper, although other materials such as cardboard, plastic, leather, canvas and board, may be used. Temporary drawings may be made on a blackboard or whiteboard, or indeed almost anything. The medium has also become popular as a means of public expression via graffiti art, because of the easy availability of permanent markers.