What Should You Do and Not Do if You See a Stranger in a Restricted Area? 
Because different workplaces can have different rules, policies and procedures for the same situation depending on what is practicable in that workplace, this is one of a series of safety posters, not aimed at educating workers in what to do, but challenging them to be sure they know what to do (and not do). And if they don't know, aren't sure, or don't remember from their safety induction or training, to find out as soon as possible.
Other issues covered in this series of posters include, what a worker should do or not do... If they see someone stealing from the workplace;  If they are offered a bribe or coerced to do something illegal; If they think someone is considering suicide;  If they are assaulted by anyone in the workplace; If they are threatened or harassed by a customer; If a fight breaks out where they are working; If someone has a medical emergency where they are working; If they are confronted by an armed thief; If the power goes off; If a fire starts; and, If the Fire Alarm goes off. There are also blank versions of this poster so workplaces can write in their own question.
 
Note that the word "authorised" in this poster is in the image so cannot be changed to US spelling "authorized".
 
An idea workplaces can use to support their responsibility in ensuring workers do know what to do and not do is various situations, is to produce small cards for lunchrooms etc which have the question on one side, and the answer on the other.