I se a lot of he/she Boas so I thought I'd esplain a quilt way of looking up your boas skirt! First off it has nothing to do with spurs! Females and males have um some are bigger then other.
you wanna hold your boa belly facing the floor (of course) with your left hand your left hand should be placed right at/before the clocaca (so?) Which is the opening on their tail with your right thumb placed on the underside grasping the tail directly behind the Copacabana run your right hand/thumb down to the tip of the tail pulling towards the ceiling in an upperward direction.
A male has two penises stored in that part of the tail when you run across them you'll feel a rubberband type pop feeling as you slide over them with a female you will feel a flat surfacewith no pop/ or movement under your thumb.
If you have several Boas I'd recommend doing it on all of them so you can get a good feel of the difference

hope I explained that OK lol