This is a small part for the Hatchbox Spool Drawers.
If you're like me, it bothers you that the stacked spools rotate freely. No prob. Just snap a few of these stays into the hinge grooves between each spool. No glue needed and they don't interfere with the drawers.
Also, you don't need four stays for each spool unless the lack of symmetry bothers you (like it does me)