I am good friends with ex-porno star/performance artist Annie Sprinkle who also lives in my neighborhood. One day Annie told me to visit the Arista Medical Supply store down the street from my studio and I would find wonderful toys. I did. The small metal clamp Katherine is putting on her nipple (#1) is actually used to clamp tubing (#2). Again, this is ornamentation to her wonderful nipples. She watches herself in the dressing room mirror tighten the clamp even more (#3) so she can let go of it with both hands and it will stay in place (#4).
But no bondage model should wear a clamp on only one nipple, so Katherine readies a second clamp (#5), positions it over her left nipple (#6), and tightens it in place (#7). Nipple clamps hurt (#8), as Kaltherine clasps her hands behind her back as a living statue to the art of submission (#9).