come in handy
To be especially useful, often in a particular setting or situation. It was a lot colder out than I thought it would be, so your jacket really came in handy! That flashlight comes in handy when I'm trying to find something in my car at night.
come in handy
[for something] to be useful. I think that this gadget will come in handy in the kitchen.
come in handy
Be useful or convenient, as in This check will really come in handy. [Mid-1800s] Also see come in, def. 4.
ˌcome in ˈhandy/ˈuseful
(informal) be useful when needed: The money my aunt gave me will come in handy to pay for my music lessons.