Watchlist screening compares arriving visitors against lists of people who should not be admitted, or whose visit needs special handling: former employees with active grievances, individuals subject to restraining orders, or names on regulatory denied-party lists in controlled industries.
Done manually it is awkward and unreliable. Done at pre-registration it is invisible: names are checked when the invite is created, security is alerted quietly on a match, and the front desk never has to make the call alone. It pairs with ITAR-style controls in regulated facilities and with plain duty-of-care everywhere else.