Graffitis is the plural of graffiti, and as such, consists of multiple instances of what is interpreted by many to be the visual appearance of the hip hop culture. Despite anti-graffiti laws, these mostly spray painted letters and pictures appear on the flat surfaces in every medium and large city. Graffitis also can appear etched upon plate glass windows, spray painted or drawn with permanent marker inside buses and trains, and in other places on both public and private property. Graffitis is normally done without any sort of permission, which makes it an illegal act. It is usually executed quickly in order to avoid getting caught by the authorities. Graffiti artists think highly of their craft, and invest a surprising about of money in spray paint, stencils, and other tools needed to get the job done. Stickers are also considered a form of graffitis.