The part that connects the spring to the plastic piece the window locks into.
Hello, thank you for posting,
Please start by reviewing the style and dimensions of the 15-104 Caradco Friction Shoe. Let us know what you think and if you have any additional questions!
Unfortunately we do not have a video demonstrating the install. You will need to remove the sashes and then the jamb liners from the window frame. The jamb liners are held in place by the sash pressing on them. You would slide out the spring with the broken friction shoe and reverse the process to install the new friction shoe. Please be careful as this can be a tricky repair. You may want to get a professional involved if not super handy.