I am trying to figure out what the corner piece of the popup is called. I have a '99 Flagstaff and each corner has this square piece. It may be to hold the two sides together...I'm not sure. These are not on top of the roof, but rather on the frame of the popup. Maybe a "Corner Cap"? The reason I ask, 3 out of 4 of them are cracked/broken. I am not sure if they really NEED to be replaced or not.