They have a knurled mounting nut unlike any I've seen before.

They're called thumb nuts and, like thumb screws, are intended to be tightened by hand (thumb and finger).

 

As you don’t need much torque, how about a piece of soft plastic tube that is slightly undersize. With the nut on the bench, press the tube on to the nut to pick it up, place on the threads and tighten, then pull the tube off.

 

We do need to tighten it pretty tight. They are used on toys and the plug is constantly being pushed in and pulled out of the jack.

 

We do need to tighten it pretty tight. They are used on toys and the plug is constantly being pushed in and pulled out of the jack.

threadlocker