Only SmartTool electronic level can measure all angles in a 360 degree range. SmartTool electronic level all ready to go in a 2 ft. The hold button makes it easy to measure in areas where the digital display is not visible. Take the measurement, push the hold button, and then bring the SmartTool in front of you to see your reading. Most levels only give you information at level (0 degrees) and plumb (90 degrees) using bubbles you have to work to center visually between two lines. You can do that with SmartTool, too, but the SmartTool also lets you measure digitally, electronically, and with an actual number, at every angle, all 360 degrees of a complete circle. So installing a deck, stair rail, extending a roof or determining how much an old floor has sagged is simpler, less time consuming, and more accurate. Welcome to the versatile world of SmartTool. If you're not dealing with plumb or level, Smart Tool quickly identifies any angle in 3 different modes: degrees, % slope and pitch. For high precision, use the digital display with amazing accuracy within 1/10 of a degree. For quick reference, use the sensitive acrylic bubbles. Smart Tool enables you to find level and plumb in two ways. UP/DOWN ARROWS - show direction of tilt to reach level or plumb.CALIBRATE - simple two-step calibration procedure (recommended once per day).LISTEN & LEVEL AUDIO - beeper will sound at level and plumb.HOLD - freeze or unfreeze display readings.ON/OFF - automatic shut-off if left idle for 6 minutes.