Just a little knob to help you open the doors, drawers and whatever else you need.
The known stick out about an inch or so, and just under an inch wide. They are a simple design that can be modified quickly should you have the need or the Solid Works software.
UPDATE!!!! 11/10.2013
So I nboticed that on good printers the hole comes out oversized for M4. On my Ultimaker it was just right for self taping. I adjusted the hole to the M4 tap drill size so All you would need to do is tap the hole and way you go.

I printed mine with low infill and came out alright actually. For the round part I would have the fan on for sure. I had mine all the way and no issues. Goes well with the paper towel holder in the background lol.
Also the hole on the bottom is 4mm diam, and I was able to run the M4 tap nicely but will accommodate anything really around that size and since its plastic you might be able to just screw it in without taping it first.
And oh yes might have to rotate the knob before you slice and print.
UPDATE!!!! 11/10.2013
So I nboticed that on good printers the hole comes out oversized for M4. On my Ultimaker it was just right for self taping. I adjusted the hole to the M4 tap drill size so All you would need to do is tap the hole and way you go.