I know, we already have cable clips. And who wants to print too many cheap little things... Still, the ones you buy are always the wrong size, and I wanted one for two different cables at once. And one in OpenSCAD would be good, right?

The STLs are for cables 7mm and 3.5mm (Power lead and phone 4-core), but you can change that stuff. Just make the diameter of the second cable (cDia) equal to 0 to print a single cable clip. Print one to test, and use Multiply to print 20! I've oriented it this way to avoid any sag. Size it to grip the cable a bit and you'll be fine. I've used a galvanised 1" nail, 'cause it's outside under the carport, and that is a nice friction fit. This was printed in PLA, but ABS may be less brittle (not that I've had any problems, with 24 doubles, 4 large and 4 small used OK).

If you want a stronger clip, make the thickness parameter (cThk) bigger to get thicker outside walls. Hey, you could use 100% infill, then you'd soon be making stronger clips than you can buy!