A keystone jack is a type of connector used to terminate twisted-pair network cables in structured cabling systems. It typically has an RJ45 connector, which is the most common type of connector used in Ethernet networks.
To install the keystone jack, it is inserted into a keystone wall plate, which is mounted in a standard wall box. The keystone jack snaps into the wall plate and is secured using a retaining clip. The cable is then terminated onto the keystone jack using a punch-down tool, which cuts and terminates the wires into the appropriate slots in the connector.