cruzomatic ,
In order to accurately measure your flaps, you need a deflection meter, as you stated as shown in the link below;
http://www.centralhobbies.com/Tools/measurement.html

jucava ,
I believe what your talking about is a deflection scale measures in inches, the other the GP laser is actually an incidence meter.

A deflection meter uses a weighted pointer and measures in degrees. Have the airplane wing level , use two and you can easily and accurately calibrate your flaps. Flaps need to be equal, otherwise your plane will drift, not good on landing. These are also great for calibrating split elevators.

Have fun,
John