"whatever you do don't forget to check the big tab is on the left and the little tab is on the right, even if you get it backwards it won't close as a safety precaution."

Gets call of machine not working in another country, sends out consultant.

Big tab is on the right, little tab is on the left and the entire tray has been forced into position because "it wasn't closing properly so we had to apply a lot of force"

Professionals with confidence are the absolute worst, I tell ever consultant or technician that comes into my lab "I'll be in the corner if you need me to grab you any supplies or coffee, do you mind if I ask questions as you go so I can have a better understanding of what's going on with this magical box". I like to think they appreciate me.