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Field guide · Cabling & termination

Keystone jacks

How to terminate a keystone jack so it certifies: how much jacket to strip, how much twist you are allowed to lose, which way the punchdown blade faces, and the handful of mistakes that account for nearly every failed test.

Plate 01Diagram

Strip, seat, punch, snap — without failing the certification.

Sequence you are laying in

Read the B row on the jack body — usually the lower of the two.

Lay-in order, position 1 through 8
  1. 1white/orange
  2. 2orange
  3. 3white/green
  4. 4blue
  5. 5white/blue
  6. 6green
  7. 7white/brown
  8. 8brown
How much twist you removed
6 mm0.24 in
Cat6 practice
Cat5e limit

Inside field practice for Cat6, and comfortably inside the Cat5e specification.

Near-end crosstalk is what the twist exists to prevent, and untwisted conductor is where it gets in. The cable manufacturer controls everything else in that measurement; this is the part that belongs to whoever is holding the jack.

Fig. 01The lay-in sequence for whichever code your site uses, and the measurement that decides whether the run certifies. Move the control to see where the half-inch allowance sits relative to what you actually left untwisted.
Plate 02Procedure

Doing it

Five minutes per jack once the sequence is habit. The failures all come from the same three places: the strip, the twist, and the blade direction.

Tools
  • Punchdown tool with the correct blade
  • Cable jacket stripper
  • Diagonal cutters
  • Cable certifier or wire-map tester
Materials
  • Keystone jacks
  • Cat5e or Cat6 solid-conductor cable
  1. 01

    Read the jack before you strip anything

    Nearly every jack is printed with both A and B colour sequences, usually on opposite sides of the body. Find the one matching your site standard and orient the jack so you are reading it, not the other one.

    CautionMixing A and B across a site is the most common cause of links that work at 100 Mb and fail at gigabit.

  2. 02

    Strip about one inch of jacket

    Score around the jacket and flex it off. One inch is enough to fan the pairs into their channels and short enough that you are not tempted to untwist further back than you should.

  3. 03

    Hold the twist to half an inch

    Fan the pairs out and lay each conductor into its channel with the twist maintained as close to the contact as it will go. TIA allows half an inch for Cat5e and less for Cat6; the crosstalk measurement is unforgiving about the difference.

  4. 04

    Punch with the cut side outward

    Seat each conductor, then drive it with the punchdown tool held square to the jack and the blade facing the waste end. One firm stroke — the tool's impact does the work, and a second pass on the same contact can fracture the conductor.

    CautionBlade backwards cuts the conductor you meant to keep. Check the direction on the first one.

  5. 05

    Fit the strain relief and test

    Snap the cap or dust cover on, dress the cable so the jacket — not the pairs — takes any pull, and snap the jack into the plate. Then wire-map it. A split pair passes a continuity check and fails a real tester.

Plate 03Questions
Questions people actually ask
How much twist can I remove at a keystone jack?
Half an inch is the working limit for Cat5e, and less for Cat6. Every extra millimetre of untwisted conductor raises near-end crosstalk, which is the measurement that fails most certifications.
Which way does the punchdown blade face?
Cut side outward, toward the waste end of the conductor. Reversed, the tool cuts the conductor on the contact side and the termination is dead as soon as you dress the cable.
Do I need a 110 tool for a keystone jack?
Most keystone jacks use 110-style insulation-displacement contacts, so a 110 blade is the right one. Tool-less jacks use a hinged cap that seats all eight conductors when you close it, and need no impact tool at all.
Can I use stranded cable in a keystone jack?
No. Insulation-displacement contacts are designed to bite into a single solid conductor. Stranded cable will appear to terminate and then fail intermittently as the strands spread under the blade.
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