Not sure if anyone else has figured this out... or not...
For those of you who know, or knew this hooray for you... for those of us a bit slower...
Most feeler gauge kits include a .0015" as part of the kit. Doubling up on the blades using the .0015" as the addition allows you to gap the standard feeler gauge blades with half sizes between each standard gauge
Example: you are measuring valve clearances and your Feeler gauge is a loose fit on .019", but .020" is a no go... double up the .018" gauge, and the .0015" and you get .0195"
