Guards popping out for a sly [blank]?

[diaglo]

changing of the guard.

potty break

a bite to eat.

a smoke

a forgotten weapon or other item

an order to run an errand.

some more money/coin as he is losing badly at cards/dice/gambling


edit: running to get some more water/alcohol for the coffee/drinks

 

[Dareoon Dalandrove]

Here's a twist Guard is in leauge with Assasins, robbers, kidnappers etc. Guard leaves their post to let others in. Depending on what the pc's are doing in this place they could get blamed for a crime they didn't commit.