A secondment is a temporary placement of an employee into another team, office or organisation, common in law, banking, consulting and government. Secondees keep their home employer while working somewhere else for months or years.
Secondees sit awkwardly in workplace systems: not visitors, not permanent staff, needing desk access, building access and often specific zones for the placement period only. Treating them as a first-class user type, with time-boxed access and booking rights, avoids both the security gap and the daily reception improvisation.