Unlike resin printers where you generally just pour the fresh resin into the easily accessible vat, FDM printers need to squirrel away at least one spool and its requisite holder somewhere. For bed slingers this generally means a top-mounted spool holder, while for CoreXY enclosed printers they can appear on the sides, top or – inexplicably – on the back. While a side-mounted spool is often convenient, access to the side can still be blocked, in which case you do what [3D Maker Noob] did and over-engineer a fancy top-mounted spool holder.The problem started after converting a Prusa Mk4S to a Core One using the conversion kit, which changes the position of the spool, forcing him to work around not having access to the right side of the machine where the default position is. After a first version using many of the left-over parts of the original Mk4S to create a fancy box-shaped spool holder, he proceeded to upgrade it as detailed in the video. All project files and instructions are available on Printables.The result is a box you stack on top of the printer somewhat like a multi-spool box, just flatter and with a flippy lid on the front from which a rail slides out with the magnetically attached spool holder. A spool holder which you naturally can further customize to fit different spools. Even if over-engineered, you can’t deny that it would fit in confined spaces and looks pretty good while doing its job.