This is a lid clip for IKEA Sortera. It attaches to the back and keps the lid in place.
Personally, I used it as a simple child lock by attaching these and turned the containers with the back side facing outwards. Worked until she was like 1 year old :-)
Prima Value PLA
Modeled with FreeCAD
I used FreeCAD to model this, and the FreeCAD file is included.