Friction. You can use a wire wrap gun that takes a bit of wire - fine-gauge, solid core, and stripped on both ends - and tightly wraps it around the square pin.

Friction. You can use a wire wrap gun that takes a bit of wire - fine-gauge, solid core, and stripped on both ends - and tightly wraps it around the square pin. A handful of turns provide plenty of surface area for the square corners of the pin to "bite" into the wire. Kind of like how in old western movies when the cowboy wants to park his horse he just loosely wraps the reins around a fencepost. It's secure enough to keep the horse from wandering off. Here's a video showing a manual wire wrap tool: https://www.youtube.com/watch?v=lG5oKLrG7R0 https://www.youtube.com/watch?v=lG5oKLrG7R0