Mesee Combination of 2 in 1 Digital Angle Finder Protractor Ruler. - Ruler and protractor combination for easy measuring length and angles. Both metric and imperial sizes laser-etched on the edge of the ruler. - LCD Display, calculating angles quickly and accurately, digital display clearly, convenient to measure and easy to read even in the darkness. - 360-degree Reversal Design, allows a full range of 0 to 360-degrees to measure inside outside and reverse angles. - Locking Knob Design, convenient to lock the angle at any position, the hold button can hold the angles at any time. - Perfect measurement tool for DIY family projects, construction projects, woodworking projects in measuring, sketching, drawing, etc. Specification: Material: Carbon Fiber + ABS. Automatically Closed Screen Time: 5 min. How to install in battery? 1. Push in the protrusion at the bottom of the LCD. 2. Pull out the battery box. 3. The negative pole of the battery is facing up and the positive pole is facing down. 4. Push the battery box back. It's recommended to take out the battery if you don't use it for a long time. Operation: - HOLD Button: "H" will appear on the upper left corner when press, the angle data will be held. To return to measure mode, pls press the HOLD button again. - ON/OFF/ZERO Button:Press this button to re-zero at any angle. Press a long time for power off. - D/M Button:Conversion between Degree and Minute. Package Included:1 X Digital Angle Ruler.