There are many variations of under desk mounts for the Mac mini M4, but I wanted something that left a little more breathing room than many of the other designs.  

Made up of 4 parts, joined together with a combination of #4 screws and dovetails, and attached to the underside of the desk with up to 8 #6 screws - certainly overkill for the support of this tiny machine.  tap tap - that ain't going anywhere…. 

I printed the parts in 100% infill PETG.  Again…overkill, but they aren't that thick.  

Optional Parts:

120mm fan.  I used a Noctua NFP-12, which I then connected to a 5v DC supply.  Running the fan at 5v slows it down a bit further, but provides enough gentle airflow to keep the heat moving away.  The combination of a high-quality fan and under-volting makes it very nearly completely inaudible - even when close to it.  Mounted under the back corner of my desk, I can't hear it all even in a silent room. 

120x120x20mm aluminum heat sink.  I found and ordered a cheap one online.  <$15.  

120x120x2mm thermal pad - to provide conductivity between the top of the the Mac mini case and the heat sink. 

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