In article
,
mike wrote:

"sewer cleanout" in the basement.

If it is indeed a sewer clean-out, a threaded, 4-inch plug is what you need.

drum trap cover

This SOUNDS like the plastic cover found over a groundwater sump (hole) in a
corner of the basement floor. Such a cover has a radius, 2-inch-wide slot to
accommodate a pump and its connections.
--

JR