Sign of a Mark

He could spot a mark from a mile away, this one however could've been spotted the next town over. A drunken fool slopping over his meal and anyone unfortunate enough to be sitting near him. This idiot, sitting there drunk off his ass, his coin purse sitting on the table for all too see, his few gold coins spilling out of it. He was an obvious target, if one of the towns thieves didn't get to him a bored patron may swipe his gold pouch. It was almost sad, this bugger wasn't leaving here with his gold and it wouldn't be because he spent too much partying the night away as he obviously intended too.
He saw an acquaintance of his sitting on the other side of the bar, he had obviously noticed the fat clown as well. He met my gaze, shaking his head and rolling eyes in mock amazement. His thumb and middle finger formed into a circle with his index finger pointed towards the fool. This was a common insult between thieves, a sly indication that a mark was almost too dumb to steal from. Of course, that wasn't true, we were, definitely, going to steal from this fool but it was fun to insult the drunkard before robbing him blind anyways. Standing up simultaneously we prepared to begin our night's work beginning with a nice easy target.
"Good evening my fellow!" I said slapping his back heartily, his glazed over eyes attempting to focus on this sudden man's arrival. So easy to distract, I thought as my accomplice casually swiped the drunks gold purse off the table. "Oh! My apologies I mistook you for another! Forgive me," bowing low, I took my leave. Idiot.

Hand Gesture

The insult is rather simple and is taught as a part of most common thieves cants. On either hand, you take your thumb and middle finger and bending them until they are touching, forming a circle. Meanwhile you take your index finger and discreetly point it towards whomever you wish to indicate is a complete fool, someone who is almost too stupid to be robbed, but of course, will be.