Question

What map tool keeps everything the correct distance apart?

Answer 1

Answer:

It’s a compass caliper. Sometimes referred to as a pair of compasses, or just compass.

Of course, when talking about maps and navigation it’s very confusing to have 2 essential instruments both called “compass” (the tool you can use to find magnetic north, and a tool to measure distances). Personally, I’d always specify “compass caliper” to avoid this confusion.