Hamish wrote:

The front plate of the letterbox has 2 receptors which accept the
bolts. The thread inside one of these receptors has completely
disintegrated, taking part of its casing with it, so it can't be
rethreaded.

How about: Knock off the rest of the broken casing and fit a standard
hex nut of the correct size and thread in its place with epoxy or car
body filler.

The reason why I suspect I may have to refill the bolt holes is
because they are *very* close to the rectangular hole and I fear that
enlarging the rectangular hole may cause it to 'merge' with the bolt
holes.

Would probably not matter if they did...

--
Cheers,

John.

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