This is a spool holder for Ikea Lack enclosure to put filament spool inside the enclosure. I pair it with my filament guide set up https://www.printables.com/model/254294-low-profile-filament-guide-for-ikea-lack-enclosure
The dovetail slot is designed for this nice spool holder from cimoalpacino https://www.printables.com/model/34288-prusa-bear-2020-spool-holder-quick-change
You will need 6x 3.5-4 tapping screws to fix it to the enclosure.
Update (09.11.2022):
Please note that this model does not fit the original IKEA Lack enclosure, since there is a thick wall part on the corner which interferes to this model. So if you are using the original design, you may check https://www.printables.com/model/313480-ikea-lack-enclosed-spool-holder-10 from Trillium_Atelier
Update (12.02.2023):
I posted the connector I made. with this connector, there will not be an interference with this spool holder.
https://www.printables.com/model/397211-ikea-lack-enclosure-top-connector
The author remixed this model.