I Googled ’Gatekeepers’ Union’, but they don’t seem to have a website. The only thing I found was a mention of gatekeepers on allefagforeninger.dk, which lists all Danish unions. The suggestions they had for gatekeepers did not include the Gatekeepers’ Union, though, only the usual ones like 3F, Krifa, MA, etc.
As a gatekeeper, you will usually be working as a guard or in the areas of security and surveillance. Similar jobs include store detective, doorkeeper and night porter.
These are all jobs I’ve never had. Unless of course they mean ‘gatekeeper’ as a metaphor. A figure of speech.
Concepts really should organize.