I just visited a counter top manufacturer in my town and I acquired a piece of slate 2”X3/4”X16” for a couple bucks. My hope is to apply a strip of sandpaper with adhesive to use it to level frets as opposed to buying the rather expensive StewMac leveling bar. When I got home, I checked how true it was by laying my notched straight edge against either side. Low and behold, on either side there is an inch or so of light escaping through the bottom of the edge by the narrowest of margins. How anal retentive should I be with the trueness of the leveler? Is the faint trace of light getting through going to nullify a fret leveling job? Thanks for the help. This will be my first attempt and I don’t want to mess it up.