At the bottom of the combination window is a little slide thing on each side corner of the bottom of the window which you push to the side to move a small post at the end of the slide which allows you to then remove the window. It is about 3 1/4 long. It is all one piece. I've bought corner pieces from you before with good luck but not one of these sliding pieces. The windows are over 60 years old and were installed by Sears I believe
Karen