I recently purchased a Beseler 23C-II. I'm the third owner that I know of and it had been setting in a garage for the past couple years. I cleaned it up and printed with it yesterday. I noticed that when the center of the image was in focus, the corners weren't. When the left corner closest to me was in focus the rest of the image wasn't, and so on. It wasn't drastic, just little tweaks to the focusing knob would put the other areas of the negative in focus but I'm assuming the enlarger is out of alignment. The print also displayed out of focus areas.
I've read in the manual how to align. I've also read people use home made laser aligners and products such as zig-align. My question is, will the method outlined in the manual, using a carpenter square and level suffice? Do the newer alignment tools available do a much better job than using a square and level?