When I first got a Peak 10X Grain Focuser, that’s when I realised that my Enlarger was not correctly aligned.

The trouble is, the Peak doesn't tell you where the misalignment comes from.

So I ended up buying a Parallel Laser Alignment Tool from Fred Newmans store

I found both my Enlarger Head and Lens Platform to be very slightly out in several planes.

To get the alignment close in one position of the head wasn't too bad, to get it close over the entire range of travel of the column and repeatedly so, was a much longer job.

Any Laser will do but getting it exactly perpendicular to your base board will require some skill