At the end of the topper there should be a little stubby arm called an anti billow arm. It sticks up at about a 45 degree angle. That plate is there to catch the anti billow arm in case it starts to unroll while your traveling, preventing the topper from un rolling.
Steve & Cheryl + Zoey, and Ziggy, our furry kids.
2012 Forrest River Lexington 283ts
Toad, 2013 Subaru XV Crosstrek