A keystone jack is a snap-in module used for mounting low-voltage electrical connectors into a keystone wall plate, patch panel, face plate or surface mount box. They allow for a clean, organized, and easy connection and help avoid a cluster of cables and visible connections to the end user.

Keystone jacks are a part of a larger connection. There are different types of keystone jacks for different uses, including audio/video, boots, Cat5e, Cat6, inline coupler, RJ 11, and USB. All keystones, regardless of the kind of jack they carry, are interchangeable and replaceable. This allows flexibility in arranging and mounting a variety of different types of electrical jacks in one plate or panel simply.