What input is this on my friends laptop?

[KurtisMash]

It is for putting a KENSINGTON lock on the laptop. It is sold seperatly and can be placed on most laptops now.

http://www.pcworld.co.uk/gbuk/kensington-combosaver-portable-laptop-lock-01063045-pdt.html

 

[dsmaster186]

It looks like a little lock with a k in it. Here's a picture http://plixi.com/p/61592617

What is it for???