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thickly painted square protrusion on round surface with cracked paint around perimeter

I noticed there is a square knob sticking out of my basement wall. Does anyone know what this is?

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  • Yes, that's what I'm going to do. Replace it with something not so bumped out of wall. Thank you very much for your help!
    – H Woo
    Jul 28 '19 at 0:02
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It looks like a sewer cleanout plug:

sewer cleanout plug

Scrape off the paint around the circle and you should be able to turn it with a wrench. Though sometimes it can be a bit hard to turn, particularly if it has been painted over and untouched for many years...

However, you might never need to remove it. You only need it if it provides a good location for cleaning a blockage in the pipes. But you definitely want to know where it is for when you really need it.

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    Thank you!!! I don't know if I want to remove it by myself now. I'd rather properly removed by professional than make a mess! Thank you so much! I couldn't figure out myself!
    – H Woo
    Jul 23 '19 at 5:27
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    @HWoo You only "remove" such plugs in order to access the pipe behind, you would never permanently remove them. Jul 23 '19 at 14:41
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    @HWoo: If it's blocking putting furniture flush against the wall or something you (or children) would potentially hit with body parts causing injury, you might be able to find a replacement that has an inset fitting for turning it rather than one sticking up like that. But indeed, you don't want to just "remove it". :-) Jul 24 '19 at 16:33
  • Yes, it's kind in a middle of the wall where I want to put my furnitures. I would replace it with something flat-style cap. Not remove it completely! :)
    – H Woo
    Jul 28 '19 at 0:04
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A less likely possibility is that you're looking at the internal head of some foundation repairs, given this is inside a basement and therefore underground.

An older building may have had extra work done to install reinforcing against quake damage or subsidence. The round part would be a load spreader (big washer).

This is more likely if there are multiple fixtures spaced evenly both horizontally and vertically over the wall. One single installation by itself is unlikely to be a tie end.

Examples - two photos of old brick walls, with retaining plates visible on the outside. These will be secured through the brick to vertical rods which have been drilled down through the entire wall.
https://c8.alamy.com/comp/B47R17/anchor-plate-or-wall-washer-in-the-old-gooderham-and-worts-distillery-B47R17.jpg via google images

This photo shows cracking in the brick around the load spreader. In a decent earthquake, this would likely fail completely.
https://c8.alamy.com/compit/bm94d6/il-vecchio-muro-di-ferro-tirante-utilizzato-per-rafforzare-vecchi-edifici-costruiti-con-soft-di-mattoni-e-malta-di-calce-bm94d6.jpg from google images

These are also installed on the other side of the wall, and can be highly decorative as well as functional. "Pattress Plate" is another name for them.

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    I believe these would not be used in a basement wall. Their typical (non-decorative) use is to keep large expanses of exterior brick from separating and bulging out of a wall. This is not the case in an interior basement. A good answer with an incorrect application.
    – Jammin4CO
    Jul 24 '19 at 21:09
  • That was my first thought as well, but ya, not likely to be found in a basement wall.
    – uhoh
    Jul 25 '19 at 8:42

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