Examples of parallelism measurement include mutual parallelism between rolls and other surfaces in papermaking machines, printing presses, rolling mills, etc. Other examples include overhead tracks, rails, press machine tables.
Easy-Laser® E975 system for roll alignment has a special angle detector, and a digital precision level. The measurement principle is simple: position the laser transmitter so that the beam points straight across the rolls, towards the detector. The vertical angle is measured first, then the horizontal. This then constitutes the reference. Then move the detector to the roll to be adjusted, or back to the roll that is to replace the old one. Point the beam towards the detector again, and adjust the roll to the correct position. Done! This method means that even short stoppages can be used for measurement.