When I'm putting guides on a rod I use a 3" level to get the seat level and then about 1/4" above where every guide is I put a piece of tape on the blank and draw a center line. That way as I wrap each guide I can just center the guide with the line. All it will leave is some very slight tweaking side to side, which is I do by eyeballing it. I've tried laser levels, strings and just about everything else I can think of and this way works best for me.