john westmore wrote:
We wish to straighten and 'position correctly' the garden fence that
we share with a neighbour in an adjoining terraced house.

What is the best way to get the fence at exactly right angles to our
houses? The garden is about twenty metres long. Thanks for advice.

As others have suggested, use the 3,4,5 rule (it's what the builders of the
pyramids in Egypt did).

If the houses are 20 meters apart, you can use 15, 20, 25 meter
measurements.

However there's one difficulty you may encounter. The wall may be square to
one house and crooked as a dog's hind leg at the other.

I recommend bushes.