What is this small component and where to put it?

During a keyboard replacement effort, when lifting the Logicboard,

I found this thing..

(In the photo you see it placed on the table next to the corner where I found it, near the Magsafe port):

I have looked at many repair guides on this website and others but I can not find where it comes from and hence where to put it during assembly now.

Who knows? Much appreciated.

Guus