putty in (one's) hands
Easy to control or bend to one's wishes. (Putty is a very malleable material.) Oh, come on, Julia is putty in our hands—we can definitely get her to help us with this prank.
(like) putty in somebody’s ˈhands
(informal) willing to do anything somebody wants or tells you to do: As soon as she starts crying, I’m putty in her hands. OPPOSITE: (as) stubborn as a mule Putty is a soft flexible substance used for fixing glass in windows.