Estimate or Service Call?

What’s the difference between an Estimate and a Service Call?
For me, it’s whether or not tools are required.

An estimate is when I come to your site, walk it with you, and you provide me with the details of what you want done.

If I have to use tools to figure out what’s wrong with something, that’s a service call. When I perform a service call, they’re flat rate, and they include a description of the problem, along with one or more solutions.