What's the 1 inch square knob sticking out of the wall?

Isto se parece com um 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 Nunca 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.

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.

Exemplos

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.