These highly opaque, lightfast and waterproof markers give your writable signs the look and feel of chalk without the mess and without the worry of rain, smudges or looking unprofessional. The chisel tip can be used at different angles to provide any line width from a fine line to a wide line. They work great on blackboards and whiteboards and can be easily removed with an ammonia based cleanser. They work on various other materials including glass, plastic, metal, wood and stone.