This thing was made with Tinkercad. Edit it online https://www.tinkercad.com/things/0w0E3Azhj3p
This mount was designed to fit Arduino Pro Mini and Pro Mini compatible boards. The PCB slides in from either end and is held in place by friction. The slide gaps in the design will accommodate the thinner style SparkFun Pro Mini PCB as well as the more common and thicker Pro Mini clones PCB's made by Baite and the like. The mount has four screw hole tabs. Enjoy!
I measured my assortment of Arduino Pro Mini and Arduino Pro Mini boards, created a flat mounting plate with four tabs with screw holes for mounting to a surface. I then attached vertical rails to the base of the mount approximately 7.0mm height (some adjustments were made along the way) figuring for an air gap below the PCB which wires can pass through and can be soldered to the top side or bottom side of the PCB solder pads on all sides of the PCB. Each rails is approximately 2.5mm in thickness so that a 1.2mm (approximate) groove could be created on each side on the interior of each vertical on the mount allowing the PCB to slide in and hold in place with a little bit of friction. To accommodate the differing heights of the PCB's found out there in the world of Arduino clones I made sure that the groove height on each rail was approximately 1.5mm so that the thicker PCB's fit as well as the thin SparkFun PCB's fit just fine.