On the E7400X, simply press the Smart Horizontal Mode key. Aim the laser at the target and press the Dist button to take the measurement.
The screen will display the angle, height, and adjusted measurement as if you took it on a level horizontal plane.
The height tracking feature allows you to take a vertical measurement continuously. This function works best on a tripod for better stability.
Press the Smart Horizontal Mode key twice. Aim the laser at the lowest vertical point and press the Dist button to take the measurement. Then move the E7400X vertically to the top of your target. A second measurement is not necessary, as the height tracking is continuously displaying the height based on the vertical angle of the Disto. Pressing the Dist button again will stop the continuous height tracking and display the last measurement.