Can't open the back/keyboard?

I have an Acer Aspire 5250-0468 (at least that's what it says on the handy dandy sticker). It's an old laptop and is mainly used for simple web browsing. Today I tried to open the computer to clean the insides, yet for some reason it kept getting stuck around the Ethernet port on the left hand side. After lots of looking through the computer and looking online for help, for the life of me I couldn't figure out if it was caught on something or there was just a clip or something holding in that needed a little bit of force.

If anyone could give me some insight I'd love to hear it. Thanks in advance!