Broken part

That's for writing in! The black piece you are searching for is the track slider for the casement hinge. This part is not sold separately so you'll need to replace the entire assembly.

I'll need to know the length of the track this piece slides in to determine the best replacement option for the hinges. 

Please let me know if you have any questions!

Thanks for confirming. Take a look over the dimensions for the 36-048 2-Bar Hinge Set. Another option is the 36-004-10 Stainless Steel 2 Bar Hinge Set. Compare them to your existing assemblies to determine which of them is the best match.

It is suggested to use both hinges from the set to replace the top and bottom hinges. Both of the recommended sets can be used to repair right and left handed applications.

Detail of 36-048

DImensions for 36-004-10