How do you find the limits of areas on a chart?

Robert M. Gary writes:

The sectional chart is used with a plotter. The plotter measures
distance and can figure direction.

I googled for this and found only software.

I presume you mean the mechanical arm-like device that I've seen being
using with flat charts on tables in movies? Certainly that might be
useful, but what about during flight? Chart tables would be awkward
in the cockpit (although large aircraft with navigators might have
them).

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