What is the purpose of putting a flange on a plug like this (from yard equipment)? Help me understand.

a flanged plug

It’s not like it’s waterproof.

It seems to me it only serves to keep you from plugging it into a cord with a built in splitter. And even with a single outlet cord, they don’t hold well.

The solutions I’ve seen are:

  1. Breaking off the flange
  2. Using a pigtail extension (e.g., 1 foot single outlet)
  3. Replacing the plug with one without a flange.

Any better options? What am I missing?

  • 2
    Extension cords for yard equipment generally come with locks that hold the plug with pins through the blade holes. Ideally you should also tie it through a strain relief buckle, or at least in a knot to keep the plug unstressed even if it gets yanked on.
    – J...
    Jan 23 at 2:34
  • This makes impossible the "coin between the plug and the socket challenge" and the related failure modes. Looks like a good thing.
    – fraxinus
    Jan 23 at 9:21
  • 1
    Another small reason for the shield around the plug's tines is to stop you plugging the device directly into a wall socket. Not sure WHY that's a good thing though.
    – Criggie
    Jan 25 at 2:39
  • @J... I've never seen an extension cord designed to lock onto the plug. I guess I've been buying mine in all the wrong places. I will seriously go look for one now, I had no idea such a thing existed!
    – FreeMan
    Jan 25 at 14:41
  • 1
    Rummages about for a CanadianTire link, wonders how much shipping to the US will be. Wonders if he can get some Tim's thrown in the box and how well they'll travel...
    – FreeMan
    Jan 25 at 14:55

3 Answers 3


The flanged plug is a UL White Book requirement

Aside from approving safe equipment, UL has a second unrelated role: they are the author of the appliance safety standards (apocryphally known as the "UL White Book").

The manufacturer doesn't want it on there. It's there because enough people got maimed or killed by appliances that didn't have it, to warrant UL changing the standards. Aand you can bet in the panel meetings, the manufacturers were banging their shoe on the table trying to stop it. But safety prevailed.

So your argument of "It's stupid and inconvenient" has already been debated and rejected by experts.

I have some guess as to why, having been bit by USA plugs that pulled half out of the socket on a power tool. But it may also have to do with not wanting you trying to use 2 tools at once or trying to drag around a second cord that's going to somewhere else.

Yes. It is a reject feature designed to inconvenience you.

And you can modify the appliance to remove it (options 1 and 3), but if you get hurt, you'll have trouble with your insurance claim. And if you hurt someone else, you will be in a much worse place to mount a civil or criminal defense.

Your best bet is probably to use an intermediate length extension cord in the middle.

  • I can live with the single outlet ended cords. The most infuriating thing is a plug that won’t hold onto a socket even with the cord attached to the strain relief AND knotted :-P. Work work 2 minutes, replug in, work 3 minutes, replug… etc.
    – BIBD
    Jan 24 at 0:26
  • 5
    @BIBD could be a bad, cheap or worn-out socket. I change them all the time. Jan 24 at 19:41
  • 2
    Would you mind expanding your answer to explain how this plug reduces the chanced of being maimed? (Or maybe "maimed" wasn't the best choice of words?) Helping reduce the chance of people getting killed or electrocuted seems spot on, but reducing the chance of people getting maimed seems a bit unlikely (albeit possible). Of course, since maimed has a few definitions, maybe you're simply thinking of a different definition than I (I'm thinking of the definition of losing a limb). Jan 25 at 8:53
  • @RockPaperLz-MaskitorCasket the shield keeps you from accidentally touching both prongs as the cord slowly unplugs itself. Therefore, no electrocution risk. Similar to the EU/UK outlets that are recessed enough that the plug pins are completely shielded from touch before (or just as) they make contact with the sockets they plug into. No power can flow through the exposed metal blades because they're never energized and exposed at the same time.
    – FreeMan
    Jan 25 at 14:43
  • @RockPaperLz-MaskitorCasket Maybe you could get an electric shock from the plug, causing your muscles to seize up and drop the chainsaw in a dangerous manner? Though I've seen these on much less dangerous tools, like a leaf-blower. Not sure how you'd seriously injure yourself with that... Jan 25 at 17:46

It prevents exposing the cord prongs when the plug is partially inserted. So when you hit the end of the cord and the device unplugs itself, there is no chance for things to contact the prongs while they are energized.

It requires the use of an extension cord. These are mostly seen only on equipment with a short cord and the expectation that a longer cord should be used with it.

If you have problems with the cord becoming unplugged, learn to properly knot them together, or buy a hunk of plastic to do the same thing. The latter are often provided with equipment using this type of plug.

The "better solution" you seek is the blindingly obvious one of using a normal-to-long extension cord with a single receptacle on the end of it, as this is clearly intended to encourage (and it might also be specified in the owner's manual.)


Flanged plugs in general

  • avoid ingress of conductive materials, like wet grass or salted snow/slush (perhaps your case)
  • avoid egress of sparks in explosion sensitive areas like gas stations, oil rigs etc...

If you replace it with an unflanged alternative, just keep it off the ground and out of the rain.

And always make sure your outdoor circuit is protected by a GFCI receptacle or breaker.

Should you require electrical protection of the prongs, due to water/grass/snow, or if the plug and receptacle keep slipping off, you could use an "extension cord safety cover"

enter image description here

If you wish to replace the appliance plug or the cord's receiving "end", make sure they are grounded, rated for outdoors, and you could opt for one with a built-in light at either end:

enter image description here


  • 1
    Can highly recommend the safety cover. I use one when cutting the hedge of similar, and it's a game-changer.
    – RedSonja
    Jan 25 at 7:45
  • “make sure they are grounded” Good in general, though there’s no ground prong on the plug in question. Jan 25 at 20:18
  • @SpencerJoplin, errr... yes, sharp observation... I mean when you get an extension cord plug and the cord is grounded, make sure the plug and receiver are grounded variants. Some look fat & bulky like they are grounded yet they are just made of empty calories.
    – P2000
    Jan 25 at 23:44

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