This is a magnetic shelf for electronic part, bathroom or kitcken,
In the bathroom you can apply it on the washing machine or dryer.

To keep it stick to a metal surface you need to screw four to six neodimium magnets with holes ( for light weight I use circular 20mm, for more increase magnet thickness or switch to square 20 x 10 ). Holes in STL are for 3mm screw.
With 3mm screw you can use nagnet with 4mm holes.

Made with PLA and 10% infill.
More DIY 3D printed parts and DIY circuits in my site: http://agalavotti.altervista.org/