I cant identify part

I need to order 2 sash immediately because i have renters coming in and window is broken. I dont trust myself doing the repair so im going to hire repair man but he said it taken him a long time to get the part so as far as the part i will take that into my hands. This window is old it was only designed for botttom part of window to go up and down. Other part is supposed to not be able to move.