For when it's hot outside and the only things you have are a PC case fan. It should fit most if not all 120mm and 140mm fans that should slot into the hole with the pin going through the mounting holes.

The angle on the part is 45° for ease of printing the pins, you can easily clone the CAD project and change the angle or remove the pins altogether in Onshape.

Print as oriented with no supports, make sure part cooling is enabled on the pins even on materials that usually do not need it.