Zelandakh, on 2012-October-04, 06:20, said:
Can you perhaps give a short write-up of what needs to be in place for it to be correct to go up with the jack here, Andy?
I've waited 25 years for this position to turn up at the table, so I don't think it's especially common, or that there are many variations. As Justin says, from East's point of view it's just a specific example of playing the card you're known to hold, and also of paying attention.