I'm not an expert either.
There is the thicker facing on the edge of the apron that the pin could go through. Although, I've been thinking of using the blanket pin I have on my kilt. I don't think I want to put that through the facing. It seems a little too close to the edge of the apron anyway.

On the thinner pins, I always put a piece of a rubberband on the pin, so it wont fall off the kilt if the clasp comes open.