"Wait, this ring has enough power for the both of us," said Katie, "We could just share it."
"Share a ring? It can only be worn on one finger," said Bobby.
"It doesn't matter who's wearing it," said Katie, "We can exchange it back and forth and we can ask each other to use it. That doesn't sound like too bad an arrangement, right?"
Bobby thought it over and said, "I suppose not, but can I have the ring now?"
"I think I need to see if I can trust you first," said Katie, "I'll wear it for the rest of today and tomorrow you can have it for a day before giving it back to me and so forth. I'll use the ring's power as you want me to, but I'll be holding onto it for right now."
Bobby gave her a hard look before sighing and said, "Fine, but I expect you to keep your end."