I am trying to mount a floating shelf. I have located two studs, 16in apart. Drilled one hole just fine, and the wall plug fit perfectly. When I drilled the other hole, my drill bit won’t go more than ~0.5in. I looked in the hole with a flashlight and it looks like metal inside? It almost looks like a metal hole. What could this be?

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I need to drill about 1inch for the wall plug to fit. If the wall plug doesn’t go all the way in, would it be alright to have it half inside the wall and half protruding? Is there a way I can secure the anchor regardless? I’m not crazy about having to remove the first successful plug and fill in the hole and start again.

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    If a wire or pipe runs through a stud, there is actually supposed to be a metal plate to prevent accidentally drilling into the stud. That matches the general nature of the problem, but I'm not sure how you would end up with a "metal hole", unless you managed to drill through it. Commented Jul 22, 2022 at 2:39
  • Also not sure what "plug" you are referring to. Normally you would use some sort of expanding anchor if you are not going into a stud, but if you are mounting directly on a stud then you use a screw through a mounting bracket into the stud. Commented Jul 22, 2022 at 2:39
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    What kind of wall are we talking about? Brick, cinderblock, poured concrete (with rebar) etc?
    – MiG
    Commented Jul 22, 2022 at 6:10
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    DO NOT PUT PLUGS INTO STUDS! Wall plugs, mollys, rawl plugs, whatever are made for mounting into drywall when you cannot find a stud in the proper location. If you have located studs and you can put screws into them, DO NOT USE ANY SORT OF PLUG, just use the screw!
    – FreeMan
    Commented Jul 22, 2022 at 11:48
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    @Ruskes Would only work if it's ferrous metal, like steel. If it were, say, aluminum, copper, etc., a magnet won't work. Commented Jul 22, 2022 at 18:48

3 Answers 3


If you are going into studs, you do not want to use those expanding anchors. You just use regular wood screws. The anchors are only needed if you aren't using studs and putting it into just drywall. Studs are a lot stronger than drywall, so if you can use studs that's the better way to mount it.

It's hard to tell from the photo exactly what you hit. It could be a drywall screw with its head broken off. Or it could be part of a metal plate that is often installed in front of wires and pipes so you don't accidentally drill into them - though I doubt you would have easily drilled a hole into that without noticing it.

  • Thank you for your answer!! That helps ease my mind a little, and I will make sure not to use the expanding anchors in anything aside from drywall.
    – Jess
    Commented Jul 22, 2022 at 12:01

You probably hit a stud guard. They are designed to protect wires and pipes that are embedded in the stud. Depending on the length of the guard, you can move up or down to avoid it.


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  • 'No longer sold at Lowes' - never seen them in UK. Seem like a good idea, though.
    – Tim
    Commented Jul 23, 2022 at 7:59

When drilling into walls, of any sort, a 'stud finder' is an absolute necessity. You could be drilling through all sorts that you don't know about - as here.

A good stud finder will differentiate between metal, wood and crucially, live wires (or water pipes). Drilling through live wires isn't only dangerous, it's a real big job to repair them. As is water pipes. Messy, too!

Firstly, you don't use the expanding anchors to fix into studs. Studs are either wood or metal, both of which will happily take screws that fix through the plasterboard, into them.

It seems you've hit an unidentified item in the wall. If possible, unless you use a proper stud finder, drill a couple of smaller (much smaller) holes, left or right, near to where you could put an anchor. If that goes well, open up, and away you go. It could be a protective sheath over water or electricity - as Grant says, or the head of a nail/screw holding the stud to something. Either way, avoid like the plague. But whatever, find somewhere else a couple of inches away, and leave that area alone. And get a good stud finder!

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    If it is something nasty to drill into that is in the stud, usually better to move up or down to miss it, instead of right or left.
    – crip659
    Commented Jul 22, 2022 at 9:56
  • @crip659 - I've found that 'something nasty' could go vertically or horizontally, 60:40 or so. In UK live wires far more often go vertically. But once again, lack of location leaves things vague.
    – Tim
    Commented Jul 22, 2022 at 11:21
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    The vertical nasties are more on the side of a stud, than though a stud. Change stud to wall then you would be right. OP stated they trying to drill into a stud.
    – crip659
    Commented Jul 22, 2022 at 11:28
  • Thank you both!! I think I will try just a bit lower and if it happens again I’ll consider it a metal plate and leave it alone/find somewhere else entirely.
    – Jess
    Commented Jul 22, 2022 at 12:03
  • @crip659 Nasties that penetrate a stud will go in the opposite direction of the stud. Nasties that don't penetrate the stud will go in the same direction--but if you aim correctly you shouldn't be touching them in the first place. Thus the only real concern is nasties in the cross direction. I have never encountered a situation where there was a horizontal piece of wood I wanted to anchor to but it's not inherently impossible. Commented Jul 24, 2022 at 14:48

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