When I'm bored, like in meetings.

 This was out the window.  To put this in context, I should  explain that I work in a psychiatric hospital.

 These were on the table.   
 I made a collegue wait to eat until I was done drawing her snack.

Sketching during meeting often prompts colleague to ask, "we're not boring you, are we?" 

To which I reply, "no, I'm good--see, I've got stuff to draw."