Punch down modules for anything permanent and keep crimped plugs for leads. A wall outlet or patch panel makes a repeatable termination, protects the fixed cable from being pulled, and lets a damaged lead be replaced without touching the run.
Both methods produce a working link. Only one of them produces an installation you will be glad of in five years.
What a module or panel gives you
A repeatable termination. Insulation-displacement contacts are designed for the job, and a punched-down module is far more forgiving than a hand-crimped plug of whether every conductor was cut to exactly the right length.
Strain relief on the fixed cable. The run is anchored in the module and the pulling happens on a patch lead. A crimped plug on the end of a solid run puts every tug directly onto the conductors in the wall.
Replaceable leads. When a lead is damaged, and one will be, you throw it away. When a crimped plug on the end of a wall run is damaged, you are back inside the wall with a crimping tool.
A tidy face. Outlets, faceplates and patch panels give you labelled ports rather than a bundle of cables leaving a hole.
What crimped plugs are for
Patch leads, made from stranded cable, for the two ends of a channel. Making your own is worthwhile for awkward lengths and for tidiness in a cabinet.
Temporary links and diagnosis.
Occasionally, a direct run into a piece of equipment where no outlet is possible — a ceiling access point, an outbuilding — and even there, a short lead into a nearby module is usually the better arrangement.
The faults each method produces
Crimping goes wrong through untwisting too much pair before the plug, using a plug meant for the other conductor type, and conductors that do not reach the end of the plug so the blades miss one.
Punching down goes wrong through untwisting too much pair as well — it is the universal fault — and through using the wrong blade orientation on the tool, so the excess conductor is not trimmed.
The published figure to respect is how much pair a module allows to be untwisted, and it is printed by the module maker. It is short. Exceeding it is the single most common reason a channel built from good components fails to meet its grade.
The pair assignment
Two published arrangements exist, T568A and T568B. They differ in which pair goes to which pins, both produce a correct link, and the only rule is that a channel uses one of them at both ends.
Pick one, use it everywhere, and write it on a label inside the cabinet so that whoever adds the next outlet does not have to guess.
Testing before the wall goes back
A wiremap tester is inexpensive and finds the fault that matters most: a split pair, where the continuity is correct but two conductors have been taken from different twisted pairs. That fault produces a link that works at low rates and fails as soon as anything faster is asked of it, and it is invisible to any test that only checks whether each pin reaches the other end.
Test every run as it is made, not all of them at the end. Finding one fault among forty finished ports is a different afternoon from finding it while the module is still in your hand.
The questions that come up before an order
Do I need a tester, or is a working link proof enough?
A link that comes up proves continuity and nothing else. A simple wiremap tester finds a swapped or split pair, which is the common fault and the one that behaves fine at low rates and fails at higher ones. Anything that certifies a channel against its grade is a different class of instrument entirely.
Does it matter whether I use the T568A or T568B pin arrangement?
Only that both ends of a channel use the same one. The two are alternative assignments of pairs to pins, and either produces a correct link. Mixing them within one channel is a fault, so pick one, write it inside the cabinet door, and use it for everything.
Last reviewed 10 September 2026