The phrase "a set of unwritten" is correct and usable in written English.
It can be used to refer to rules, norms, or guidelines that are understood but not formally documented.
Example: "In our organization, there is a set of unwritten rules that everyone seems to follow, even if they are not explicitly stated."
Alternatives: "a collection of implicit" or "a group of unspoken".
In most hospital settings there seemed to be a set of unwritten rules for clerks.
Doctors and patients say the bribery follows a set of unwritten rules.
There's a set of unwritten rules there, and I don't understand them.
She appears to have followed a set of unwritten rules about the comportment of women attached to important men.
"Goose and his peers developed a set of unwritten understandings about what was acceptable on the field when he played the game, and I think the generation of players that are on the field today are going to do the same thing.
Studying how nonscientists order and name life, creating what are called folk taxonomies, anthropologists began to realize that when people across the globe were creating ordered groups and giving names to what lived around them, they followed highly stereotyped patterns, appearing unconsciously to follow a set of unwritten rules.
He has devised a set of heretofore unwritten rules whose numbers he and his aides call out during meetings, to the bafflement of the unknowing.
Just as living in a society requires us to follow a set of conventions (unwritten but well understood expectations) and rules, observing appropriate social behavior within the work context ensures congeniality, team respect and an enjoyable day-to-day working experience.
Dancehall is actually governed by a rigid set of unwritten rules.
They demonstrated the strange set of unwritten rules among chess players by upsetting an opponent irrationally by simply exchanging pawns without any alteration in position.
The NBA has its own set of unwritten rules involving manhood.
