Tell me about a time your project was blocked by another team. How did you unblock it without damaging the relationship?

Imagine you're building a treehouse with friends, but one friend has the only hammer and keeps forgetting to bring it. You can't just grab the hammer without asking, or they'll get upset. So you talk to them, find out why they're late, and maybe offer to help carry their tools next time. That's what this question is about: solving a problem without making enemies.