up one's sleeve

From the practice of magicians hiding tricks or gimmicks in the sleeve.

• "I have tried everything I can think of, and I don't have anything more up my sleeve."
• ""There may be things that you know which I do not. I have not pretended to be aware of all the details of your show. But equally I've got something up my sleeve that you don't know about. And that's where I mean to score. Danvers was a damned clever fellow——" He broke off as if he had said too much."

• nothing-up-my-sleeve number
• roll up one's sleeves