Qualification
A qualification is a skill, a certificate or a permission that a position can require: a bar licence, key holder, trained on a particular room. People hold qualifications, and positions require them.
Why it matters in a small workplace
It is the rule broken by accident more than any other, because nothing about a name written in a cell says what that person is actually allowed to do.
How Weeksort handles it
Give somebody their qualifications once and require them on the position. Weeksort then offers you only the people who can work the slot in front of you — and it narrows as well as widens, because a junior position can require something senior staff do not hold.