what type of lens board.?

What is this screw on flange for.?
I have one of these boards, but the few lens i have (as far as i know) do not need this fitting.
What lens Would Require This.?
Thank You

http://www.ebay.com/itm/BESELER-LEN...e=STRK:MEBIDX:IT&_trksid=p2055119.m1438.l2649

It's for the longer focal length lenses like 105 and 135. My normal lens board works fine for a 105mm lens, although it would be easier to make small 5x7 prints from 6x9 negatives if I had this extension ( I'm right at the end of the bellows when I print that small ). Also see here.