HEDÜ M-I Mode D'emploi page 22

Checking the horizontal line
Put the HEDÜ M-I or HEDÜ M-IIS in a distance of 5 m in
front of a wall. Mark the intersection point of both laser lines
as point A.
Turn the laser right and mark point B. The distance between
A and B shall amount no more than 1.5 mm.
Turn the laser left and mark point C The distance between
A and C shall amount no more than 1.5 mm.
22 22
5 m
A
A
B
C
A
B
.