Where is the laptop lid switch?

I replaced my Sony Vaio VGN-Z520n HD recently with a SSD and the laptop no longer goes into a sleep mode when I close the lid. I'm sure there is just some type of switch that lets the laptop know the lid is down but I cannot seem to find where it is to adjust it back into place.

I was able to find it. It is located on the lower left corner of the laptop. it had a small ribbon cable connected to it that I overlooked when I was putting it back together.

Thanks for the tips oldturkey03