Before using it, you must first make a school pair, calibrate the spirit level tools
. Place it on a flat wall, draw a line, call the horizontal ruler, put it on the line you originally painted. If it is capable of coincidence, it is also possible to ensure that the measured data is also accurate.
We need to use it when the wall is flat, it can be measured short distance, and it is possible to perform long-distance measurements, and it is relatively high.
Before use, there is also a need to detect the horizontal ruler with a crack, a pore, and place the spirit level tools on the object to be tested. If a part of it is biased, it indicates that there are some high, and you can reduce the height of this side. If the blisters are in the center position, this direction is horizontal.