She slaps his ass on his way to the chair- because how else is she going to know for sure? All she's had a look at before is his chassi- which is very nicely shaped, as it turns out. And apparently real life don't change that much about a boy.

"You're hot as hell, and you know it." Harley tosses her bathrobe on the bed, to settle in Jack's lap with her own joint and the lighter. She slings her legs over the arm of the chair, letting them kick idly into the air. "Tall, and lean- strong jaw, great hair -" One finger trails along his cheek, on the non-mask side. "And your eyes are two different colours. I figured they'd be blue." The smile that tugs at her mouth is wide and easy; this close she can really look at him, taking in every inch. That mask really is incredible. "And a great attitude, which really is the most important part."

This time she touches the masked side of his cheek, letting one fingertip trail down. "You can feel this, right?"