It's in the basement floor but lacks the rubber "meat cleat" of a test cap. The bolt head is out of sight, and I'm afraid to completely take off the wing nut without getting creative for keeping the bolt from falling into, presumably, the cast iron sewer line under it.
When I unscrew it to peek in, there is a metal plate stuck inside what looks like a cast iron flange. It cannot be pried up.
So, I don't know what it is, what purpose it serves, and how to get it out. Could you help me figure it out, please? TIA!!
Pictures are at:
https://i.imgsafe.org/d4dfd2764c.jpg
https://i.imgsafe.org/d4e01568a8.jpg
https://i.imgsafe.org/d4e06737ea.jpg
ps- I needed to get under it to learn more about a complete blockage of the 40 year old rough-in shower stub three feet to its left (which I discovered was completely blocked with ??? when trying to learn about why, for the first time, the washing machine discharge drain three feet to its left is draining too slowly for the same washing machine that has been there for 9 years. (I snaked it to no avail.)
When I unscrew it to peek in, there is a metal plate stuck inside what looks like a cast iron flange. It cannot be pried up.
So, I don't know what it is, what purpose it serves, and how to get it out. Could you help me figure it out, please? TIA!!
Pictures are at:
https://i.imgsafe.org/d4dfd2764c.jpg
https://i.imgsafe.org/d4e01568a8.jpg
https://i.imgsafe.org/d4e06737ea.jpg
ps- I needed to get under it to learn more about a complete blockage of the 40 year old rough-in shower stub three feet to its left (which I discovered was completely blocked with ??? when trying to learn about why, for the first time, the washing machine discharge drain three feet to its left is draining too slowly for the same washing machine that has been there for 9 years. (I snaked it to no avail.)