First ask permission! Some men are shy about stuff…
Make sure its an appropriate time and location, i.e. NOT in church or work!
Stand behind the kilted one and place your hand on the OUTER side of his knee.
Slide your hand up the OUTER thigh, feeling for underwear material (example: boxers) Use your free hand to make sure his kilt doesn’t “ride up” while you do this.
For a more genteel check, (Not Recommended) run the edge of your thumbnail up the outer thigh, OUTSIDE of the kilt, feeling for the “speed bump” that indicates undies.
Don’t be all day about it! A 5 to 10 count “up”, 5-10 count “at the top”, 5-10 count “down” should be more than sufficent! It’s not as if its hard to tell if its skin or skivvies, 30 seconds and the job *should* be done, even with “lingering”.
If the man is indeed regimental (meaning you felt no undergarment material) then declare him to be so. Anything more is a different game!