As the slide moves rearward, a ramp on the inside of the slide forces the connector inward, allowing the trigger bar to be pulled upward by the trigger spring. As it comes up, the bar overlaps the guide angle on the connector. As the slide comes forward, the connector is allowed to move back outward, but it is now blocked by the trigger bar. As you release the trigger, it moves forward, and the connector clicks back out. The shape of the guide angle and the trigger bar will affect how abruptly it clicks outward.