This minimalistic mount allows to attach 140 mm fan on top of two 3.5 HDDs inserted into Odroid HC4 in official toaster case.

Such construction allows for prolonged heavy duty working with HDDs without risk of them getting overheated, if natural convection cooling is not enough, with minimal amount of materials required.

To connect fan to 12V you need either to solder jumper wires to HC4 (there are two +12V test pads) or use separate 12V power supply, or use a DC step down converter.