Material: High-quality Crack Gauge Monitor is made of high-quality acrylic material, so it is durable, sturdy, smooth, wear-resistant, and not easy to break. Clear and Precise: Crack Monitor is designed with a highly clear acrylic sheet and an easy-to-read measurement grid, so it is clear and precise. It is very practical. ✡Cracks: Corner Crack Monitor is a simple and cool analog cracks and a precision instrument used to monitor the horizontal or vertical movement of cracks on a plane. ✡ Monitor the evolution process: Cracks are used to monitor cracks in walls and the process of evolution over the measured time. It is very convenient for you. ✡ Smart design: The crack measurement consists of two boards that overlap one part of their length. The lower one is calibrated in millimeters, and the upper one is transparent and marked with a fine-line slider in the shape of a cross.