I had a look at Jira's Kanban board a week ago and while it is what everybody else seems to implement as an electronic Kanban board, one can't do Kanban with it like Henrik Kniberg did in Lean from the trenches.
And I don't think much has changed since Kniberg's Jira rant: "I don't hate many things. But Jira... it's like a cancer that sucks the soul out of companies. Even w Greenhopper. #uxfail" (Greenhopper being the Kanban board Jira bought.)
As the time of writing, one can only resize the two rectangles.