These brakes can be accurately adjusted using a cheap dial caliper. Example: if you have a 10 inch drum, the distance from center of axle to contact area of shoe is 5 inches. Since you cannot measure from center of axle, add 1/2 axle diameter to 5 inches, and measure from outer edge of axle to outer edge of shoe. Very simple, very easy, very cheap, and it works good. No expensive tool needed. Subtract desired shoe clearance from 1/2 drum inner diameter, add 1/2 axle diameter. 10 inch drum, with 1 inch axle, and .010 clearance equals 5.490 reading on dial caliper.