Magnetic shelf holder

Magnetic holder attached to a shelf. I created this thing to set my speaker under a shelf without using screws or any kind of adhesive, so no harm it's done to the shelf or the speaker. Also, the speaker can be oriented easily. But I think it can be used for more purposes.

I used a 5 cent Euro coin because it can be attracted to a magnet. You can find a magnet easily inside a hard disk drive. Two magnets are enough to hold the speaker and can be hidden with the piece "cover". You also need two screws to attach the holder to the shelf.