Escort Visitors
Escort visitors and monitor visitor activity. Any non-employee must be monitored with an authorized employee at all times.
Example
Coming back from a meeting, you see the friend of a coworker walking down the hallway near your office. You know this person well and trust them, but are not sure why they are in the building. You stop to talk, and the person explains that they are meeting a coworker for lunch, but cannot remember where the lunchroom is. You walk the person back to the reception area
to get a visitor badge and wait until someone can escort them to the lunch room [a]. You report this incident and the company decides to install a badge reader at the main door so visitors cannot enter without an escort [a].
References
NIST SP 800-171r2 3.10.3
https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-171r2.pdf