I measured the blade gap using a set of feeler gauges. However, measuring the blade gap is mostly an academic issue. If there's a blade gap issue, you will most likely be able to see it with the naked eye (I could definitely see the blade gap issue with the DeFitch razor). I'm not an expert on the Merkur razors, so you might want to post this question in tomorrow's (Wednesday's) General Questions thread. But which Merkur do you have and what type of issue are you having?

Not sure of the specific feelers are included in the feeler gauge you provided but I used this one to adjust my valves correctly. http://www.amazon.com/Lisle-68100-Deluxe-Feeler-Gauge/dp/B0009OMY9C

Let me know if you have any questions. Had to replace I believe around 4 shims; did the can swap mod for first gen sv.