"dpb" wrote:

_NOT_ runout; totally different measurement.

I'll mostly echo Morgans' response but w/ a slightly different
suggestion...

Presuming the bolt locations are symmetric, measuring the diagonals
would be easier to determine the amount off and in which direction.

Then knowing that, put a bolt well into the two locations on the
longer
measurementand use a heavy wire loop and then twisting will shorten
that
dimension. Release and repeat measurement until stays in desired
location; you'll undoubtedly have to go a little extra with the
inevitable spring-back.
snip
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SFWIW, the above describes what is known as a "Spanish Windlass".

Very useful on a boat when a winch isn't available.

Lew