Rock writings, like all symbolism, may look like art but speak different languages depending on the interpreter. Petroglyphs are symbols made upon rock by pecking, incising, abrading, or scratching. Pecking is striking a tool against the face of a rock, either directly against the rock face or indirectly by placing one tool against the rock face and striking its other end with a second tool. Incising and scratching use a sharp or pointed tool to create lines with a V-shaped cross section. Abrading rubs a tool back and forth along the rock face to create a smooth surface. Pictographs are symbols painted upon any material. A petroglyph panel is a symbol or group of symbols conveying a message, either complete in itself or related to other panels nearby.