In message , Frank Stacey
writes
I want to remove a bolt which takes a 4mm hex alan key - well it's not
quite that simple. The hex hole has a central pin which prevents the
insertion of a standard alan key. It may be a useful security feature
but nobody knows the wherabouts of a suitable key so it's a problem.

Ayone know if suitable alan keys can be obtained anywhere? I can't
find such things via screwfix.

It's a Torx Security bolt

--
geoff