Can anybody tell me what this is?

[Suggy]

I recently returned from holiday on a Boeing 737 300/500 and noticed a 'disc like' protrusion on the flap fairing on take off which retrated later. I have no idea what it is. I found a picture on airliners.net which shows this.

http://www.airliners.net/open.file/1039380/L/

Does anybody know what it is?

Thanks,

Darren

[Joe Cygan]

That is a retractable landing light.