How to Punch Down a Keystone Jack

A keystone jack is a small part that decides whether a whole run passes or fails. Knowing how to punch down a keystone jack properly means the link tests clean first time, with no callback to re-terminate a wall plate. This guide walks through each step, from stripping the jacket to testing, and explains which mistakes a simple continuity check will miss.

Tools and parts for keystone jack termination

Lay everything out before you open the box. A punch-down keystone jack needs very little, but each item matters:

• A 110 punch-down tool with a cutting blade. Many tools have an impact setting; use the one the jack’s instructions ask for.
• A cable jacket stripper that scores the jacket without nicking the conductors.
• Flush cutters for the Cat6 spline and any conductor ends the tool leaves.
• Jacks rated for the cable category, plus the wall plate or patch panel they snap into.
• A tester. At minimum a wiremap tester; ideally one that can find split pairs.

Most punch-down jacks are made for solid-conductor horizontal cable, so check the gauge range on the jack’s packaging before you start. The cable itself is covered in our guide to Cat5e vs Cat6 for security camera runs, and bulk cable is in the bulk wire category.

Step 1: strip the jacket and prepare the pairs

Score the jacket and pull it off, then look closely at the conductors. A nicked conductor can break or short later, so cut it back and start again if you see bright copper through the insulation.

The Fiber Optic Association’s UTP termination reference says it is good practice to minimise both the untwist and the length of jacket removed. Strip enough to handle the pairs comfortably; the jacket should end up as close to the back of the jack as the jack allows.

• If the cable has a plastic spline, as many Cat6 cables do, trim it flush with the end of the jacket.
• Remove the rip cord the same way.
• Fan the four pairs out but leave each pair twisted for now.

Step 2: follow the colour label for Cat6 keystone jack wiring

Every punch-down jack has a colour code printed or moulded beside its slots, usually with an A row and a B row. Pick one scheme and use it at both ends of the run. The FOA reference is blunt about it: always follow the colour codes on the back of the jack, because the slot order varies between jack designs.

The pin-by-pin order and the reasons to pick one scheme over the other are in our T568A vs T568B wiring guide, so there is no need to memorise them here. What matters at the jack is that each pair lands in its own pair of slots, side by side, exactly as the label shows.

Cat6 keystone jack wiring is the same in principle as Cat5e, but the conductors are often thicker and the jack may include a wire guide or lacing cap. Use it if it is supplied; it holds the pairs in position while you punch.

Step 3: how to punch down a keystone jack with a 110 tool

Untwist each pair only as far as it needs to reach its two slots. The FOA reference gives the maximum untwisted length for Cat 5, 5e, 6 and 6A cable as 0.5 inch (13 mm) and says the twists must stay as close to the receptacle as possible to limit crosstalk. Treat half an inch as a ceiling, not a target.

1. Rest the jack on a firm surface or in a punch-down holder so it cannot rock.
2. Press each conductor lightly into its slot by hand, with the tail running past the outside edge.
3. Place the tool straight down over the slot with the blade side toward the outside of the jack, where the waste end is. A reversed blade cuts the conductor inside the jack.
4. Push until the tool releases. The conductor should sit fully down in the contact and the tail should be cut clean.
5. Work one side, then the other, so the pairs stay in place.

If a conductor lifts back out or the cut is ragged, re-terminate rather than punching the same spot over and over. A strand nicked by a bad punch may test fine today and fail later.

Step 4: cap the jack and mount it

Trim any tails the tool left, check that no copper sticks out beyond the contacts, and press the cap or dust cover on until it locks. Then snap the jack into the wall plate or patch panel from the back.

Watch the cable behind the jack. A tight bend straight out of the back of a shallow box strains the pairs right where they leave the jacket. The FOA warns that bending too tightly can harm frequency performance, and that Cat 6 and 6A need a larger bend radius than Cat 5e. Bend radius figures and rack-side routing are in our guide to network rack cable management; plates, boxes and straps are in the wire and cable management category.

Step 5: test every keystone jack termination

A link that lights up is not a link that passes. The FOA’s UTP wiremapping page explains that a wiremap confirms each wire is terminated correctly with no opens or shorts, but a split pair will still pass a simple DC wiremap while failing crosstalk. Finding it takes a more capable wiremapper or a category tester.

Test each run end to end, label both ends, and record the result before you close up the wall.

Common termination faults and their fixes

Most failed jacks come down to a handful of faults. The table matches each one to its usual cause and to the test that shows it.

A run that maps correctly but fails a performance test usually points to too much untwist, a kinked cable behind the plate, or a jack of a lower category than the cable.

Where to find keystone jacks and supplies

Termination parts are grouped in the Bursma connectors category, and the wider wire, cables and connectors division covers cable, finished cords and management. Blank and F connector inserts for mixed plates are listed under keystone wall plates and inserts. For jacket ratings on runs through risers or plenums, see CMR vs CMP cable explained.

For pricing and availability, ask your sales representative through the Bursma contact page, or call the Wyoming, Michigan branch. If you install for a living, apply for a Bursma dealer account.

Frequently asked questions