Small 240x125mm shelf for a router or modem that can be hung on a 19mm wide ledge.
You'll need 4x M3 square nuts and 4x M3x8 or 4x M3x10 screws; grab them from the printer's spare bag if you still have it.
Put the nuts into the hooks' holes; if they don't fit, use the screw pulling technique just like you did while assembling your MK3S printer. Stick all parts together, tighten the screws and hang the assembled shelf anywhere you like.
The author marked this model as their own original creation.