Keystone jacks are small inserts designed to snap into place on keystone wall plates, patch panels, and surface mount boxes. Equipment built for keystones will have small holes left in them instead of having jacks pre-built in. Keystone jacks snap into place in these holes, allowing users to customize what jacks are included however they see fit. Keystones are also easy to remove if anything ever needs to be repaired or replaced.

A standard keystone wall plate, designed to accept four keystone jacks

Punchdown vs. Coupler

There are multiple types of keystone jacks available, primarily consisting of various types of voice, data, audio, and video connections. Additionally, keystones are available in both punchdown and coupler formats. Voice and data keystones can be either one of these while audio and video keystones are typically only available as couplers.

The difference between the two types lies with how cables are connected to the back of the keystone jack. Punchdowns allow bare wires to be connected to the jack. Directly wiring into a jack is most commonly used for permanent installations. Couplers allow a cable to plug into the back of the jack, the same way something plugs into the front side. These couplers (and the cables connected to them) can be removed and replaced easily.


A top view of a punchdown keystone (left) vs. a back view of a coupler keystone (right)

Voice and Data (Telephone and Ethernet) Keystone Jacks

Ethernet jacks are the most common type of keystone. Since all ethernet cables use RJ45 connectors, these jacks are the same size and can be hard to tell apart at a glance. Some manufacturers will have the front of the jack labeled as Cat5e, Cat6, etc. but this is not a universal rule. Be sure to check the description of a keystone jack before ordering.

Ethernet can be a bit tricky compared to other keystones because there are different versions available. If a keystone jack is simply labeled “keystone”, that means it is a standard keystone. Some companies make their own versions of keystones that are a slightly different size from normal. Examples include ICC’s High Density Jacks and Panduit’s Mini-Com Jacks. Standard jacks will not fit into equipment rated for non-standard jacks, and vice versa. If you pick one piece of equipment that uses a non-standard jack, the rest of your setup needs to be rated for that same kind of keystone jack.

Telephone keystones are similar to ethernet, looking like downsized versions of the same thing. Like ethernet, RJ11 and RJ12 are hard to tell apart by just looking, so keep an eye on those product descriptions. Also like ethernet, there are some oddball versions of telephone jacks available (most notably ICC’s High Density line).

Audio and Video Keystone Jacks

Audio and video keystone jacks cover many of the most common types of audio/video connections used today:

  • 3.5mm
  • BNC
  • F-type
  • HDMI
  • Optical Toslink
  • RCA
  • S-Video
  • Speaker Wire

Most of these keystones are only available as couplers, with the exception of speaker wire jacks (more details on speaker wire connections here) and 3.5mm push pin jacks. Full details on each type of audio/video cable can be seen here.

Push pin

The back of a 3.5mm keystone coupler (left) vs. a 3.5mm keystone push-pin (right)

The one disadvantage keystones have on audio/video connections is their size. Larger types of connections such as VGA, DVI, and DisplayPort are simply too big to fit onto a keystone jack. Users can work around this by using an adapter to go from a keystone supported format to the one they do need. For example, if you need to plug into a DVI monitor you could install HDMI keystones and use an HDMI to DVI cable. Keystones may have their limitations, but a little ingenuity usually lets you find a workaround.

Blank and Feed-Thru Keystone Inserts

While keystone jacks are common, they are not the only option for an installation. Sometimes, there may be extra keystone holes left open which can be plugged up with a blank insert. Since keystones are easily removed, a blank cover can keep dust out while leaving space available for future upgrades.

Using a keystone jack may not always be the most convenient option either. When working with long pre-existing cables, it may be easier to use a feed-thru insert. These little inserts can hold a cable in place and stop it from wiggling around, reducing wear and tear over time.

Feed through

A blank keystone (left) vs. a feed-thru keystone (right)

Keystone Tools

Wiring a keystone jack can be a little tricky due to their small size. Though it may not be 100% necessary like a standard punchdown tool, using a keystone punchdown holder makes the job a lot easier. These handy little holders act like a second pair of hands, keeping the keystone jack steady so you can easily get the wires punched down.