If you are in the US, you can find digital calipers from Harbor Freight for around $5.
+1 on that video, I never really understood how to measure the gap but now I do. So easy.
Kyosho V-One RRR - JP Modified Mugen X12 - GQ Racing Tires - Futaba servos - KO Helios w/Spektrum Pro - Maxy's Fuel
Losi 8ight 2.0 RTR for fun times