This is a simple, cheap method for destroying old hard drives, making the data unrecoverable against casual attackers and identity fraudsters (although probably not some hypothetical government agency with multi-million dollar resources).
For this you will need a stack of old hard drives:
An electric drill with a twist drill bit (suitable for going through metal), and most importantly some eye protection:
Line up the hard drives against the wall and drill straight through them. I didn't show it in this picture, but in fact I drilled through from the other (PCB) side to ensure that I went through the PCB but didn't go through any components that might explode:
Sunlight where there's not supposed to be sunlight!
For a few of the drives, mainly older ones, I couldn't get all the way through, but I got through to the platters, which is the important part:
Now you can see why eye protection is not optional. This old IBM SCSI-LVD drive had glass platters which shattered into tiny, sharp shards of metal-plated glass when the drill went through:
For extra assurance, I will soak the drives in a bucket of water for a few days before disposing of them: