When to use it
Use it when you're asked to take on something outside your usual work and your plate is already full. You stay helpful, and you make the trade-off visible: something else has to move. Your manager decides what moves, which is their job.
Example
Manager: “Can you handle the vendor calls this week?”
You: “I can take that on. What should I move to make room?”
Manager: “Push the report to next week.”
In an email or Slack message
In writing: “Happy to take on the vendor calls. To fit them in, I'd push the Q3 report to next Tuesday. Does that work?” Proposing what moves saves a round trip.