window part

Hi, I like to find out a part of a window.

The part I'm talking about is at the center of the photo which is tighten by the screw. They are located on each of the top corners of a sash. Their purpose to hold the spring or coil casing(located on both sides of the window) as the sash is being push down. I'm not sure of the brand of the window, but a window repair buy told me it might be a Capital window.

Please advice, Thank you