This will usually be the second position he will assume after Waiting. His hands behinds his back, at least stripped to the waist (if not fully naked) he will present his body for your inspection. Make sure that he holds himself very straight, doing a hollow back, in no case bent forward or with a round back. His whole body must speak of tension, readiness, awareness, attendence for you.
The meaning of the Mistress’s gesture to symbolize the position is obvious. Her two opening and closing fingers silently say “Spread your legs … make yourself available for My inspection”.