Acer Xb281hk / XB 271HK Stand or Base help

[Johnsmith45]

I have a acer xb281hk. My question is regarding the stand. There is this black piece on top of the stand that goes into place which stops the monitor from moving. It basically locks the monitor into place. It looks like a piece of triangle or lid. 

 

https://www.google.com/search?rlz=1C5CHFA_enGB853GB853&biw=1440&bih=821&tbm=isch&sxsrf=ACYBGNSb3CKNk1s_IYGS7rirCywoh87K3Q%3A1572004351912&sa=1&ei=_-GyXfagN6yQlwTh2LrABQ&q=acer+xb281hk+stand+back&oq=acer+xb281hk+stand+back&gs_l=img.3...66183.67306..67595...0.0..0.54.221.5......0....1..gws-wiz-img.-WPZRJEg5IY&ved=0ahUKEwi2nOzHrLflAhUsyIUKHWGsDlgQ4dUDCAc&uact=5#imgrc=kL7BCgn2HUFEAM: 

 

Any ideas what that is called.