Whiteboard pens are often laying scattered around the room. To attach them neatly to a magnetic board, this model is intended.
The indents on the one side are for gluing in three small neodym magnets (12 x 1 mm or 12 x 2 mm), which then fix the holder on the board.
The second design uses a strip of magnetic tape.
0.2 mm, PLA, no support
The author hasn't provided the model origin yet.