Highlighting text
 

Hi everyone, I would like to ask how if there is way to obtain the highlight text effect on Omnigraffle..something like this:
[url]http://d3pr5r64n04s3o.cloudfront.net/tuts/385_omnigraffle/preview.png[/url]

the irregular one, not just simply the yellow background.
It is probably something very easy, but I really cannot figure it out!