I've checked the archives but I could not find any discussion of the
sink.  If I missed it, could you please point me to the discussion.

I am trying to clean out the sink trap (immediately below, and
attached to the sink) and I don't know how to take the plastic
mechanism apart.  Does it come apart? and how?

Also there is a small metal 'tab' at the base of the trap,  what is
this?  Does it come out, unscrew?

Thanks.   Malcolm