Officemate Plastic Hanging File Frames, Letter and Legal Size, Rails 24 to 27, 2 Sets (91963), Black

I think I know what this is, or at least something similar. I purchased file hanging frames rails to hold file folders and they adjust to the size of your drawer. You break them off at the correct length. You can see them with the rails here. Looked exactly like this. https://a.co/d/0aW2IwSQ