hmmmm....
I have learned to REALLY consider a specialized ruler of any kind before buying. I have so many that I haven't even used. So now when I am at shows, I ask for the business card, write the booth number and name/description of what I think I want. After the shopping part of the show, if I really want it, I go back. If I am not sure, then I don't buy it. I do, however, still have their info in case I change my mind after I get home.