well, razor comb is a comb with razor blades in the teeth and as you comb it through your hair you will cut hairs. the lighter you comb the less cut. the key is to trim away at the ends of the unit hair to blend it into your own hair with frequent stops where you comb your hair with a regular comb and re-evaluate where to trim next. you need a hand mirror and a wall mirror. you can do a muth better job than a salon person with those dreaded thinning shears...never never use them in my opinion. gel