The vertical alignment of the shafts to the base of the dissolution bath is critical to the correct operation of the system. From an adjustment point of view, there is little that the user can do about it and it should be set by the manufacturer.
However, the ASTM validation guidelines require that vertical alignment is tested as part of the physical testing routine, and it should not be ignored.
The simplest method to check vertical alignment is with a set square available from any tool store, but that is not an actual measurement. Digital vertcality testers are now available as well that conform to the ASTM requirements. Remove the vessels and lower the shaft until it is just below the base plate. Take the square and align it with the base and shaft to check the vertical alignment of the shaft. This should always be checked by the manufacturer on installation because physical trauma can occur during shipping. If an error is found then the manufacturer should be contacted to correct the problem.