gain the upper hand
When you get the best part of a girl’s hand, the upper one, during a lazy day, and you just won’t let it go.
He got her upper hand while they were eating pizza. She tried to take it back, but he just laughed.
She was lazy on the couch, and he grabbed her upper hand like it was a trophy.
He had her upper hand the whole time. She said he was a hand thief.