junction box

My can light junction box has 2 black clamps for NM cables and there are 3 metal knockout holes on 3 sides of junction box. (Picture shows one of these 3 knockouts).

Given the location of LINE wire and can light locations in celling, can I attach 3 NM (romex) cables with one can light ? Can light junction box has only 2 clamps , but can I use knockout hole ( metal) for 3rd cable? All cables are NM cables

1 LINE cable (through Knockout holes)

2 cables connecting to 2 other can lights. ( Through black clamps)

Take a look at diagram with red color can in question.

enter image description here

  • 3
    Is that box marked with a volume (cubic inches) anywhere? Nov 27, 2020 at 16:34
  • I agree, I know the problem seems "solved" to you OP, but the "cubic inch" question is important, and may be a deal-killer. We need to know. Nov 27, 2020 at 19:01
  • It does say max 8 14 AWG conductors on junction box. Nov 27, 2020 at 23:14

2 Answers 2


You have to use something when ever NM cable enters a metal box or enclosure to protect the cable from abrasion.

If you use a clamp for two cables, it must be rated for two cables of the applicable size. For example the Arlington NM94 is made for a 1/2" trade size knockout and can be used with one or two 14/2 or 12/2 NM cables.

Arlington NM94


Yes, you just need to add an appropriate clamp, like:

NM clamp

You should be able to get them at any hardware store/home improvement big box store/etc. An electrical supply house will be cheaper, but for an occasional clamp just go "anywhere".

  • I have one like this one already. Would it work ? Check out link. tinyurl.com/y5hyk7sa Nov 27, 2020 at 16:16
  • That's a different style but perfectly fine. The only question is whether it matches the knockout size. Nov 27, 2020 at 16:25
  • 2
    @user2716454 Yes, that clamp indicates it is meant for this purpose (securing NM-B cable in 1/2 knockout). Nov 27, 2020 at 16:25
  • 1
    I am pretty sure the clamp in the picture is actually rated for just one cable. Nov 27, 2020 at 17:39
  • 1
    @batsplatsterson Just read the question again: "can I use knockout hole ( metal) for 3rd cable" So my answer works. That being said, sometimes it is easier if the cables all enter through the same location, so your answer is good too. Nov 27, 2020 at 18:07

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