On Mon, 01 Apr 2013 00:18:46 -0500 Vic Smith wrote:
I never saw a kitchen P-trap with a built-in clean-out.

That's interesting!
How are we supposed to clean them out then?

The sink drain basket size and sink line size determine drain
trap piping size. 1 1/2' is common and enough.

Oh. OK. Makes sense.
All I had known was the current size clogged from a woman doing normal
kitchen chores.

Your rusty nipple goes into a 1 1/2" T in the wall.
That has vent pipe above and sink line below.

Should I be worried about twisting the rusty nipple and ending up
damaging the T in the wall (which would be difficult to get to because
the built in kitchen cabinet sink is in front of it).

Remove the trap and clean it.

OK. I guess that explains why there was no way I could get a snake into
that kitchen sink from the top.

Internal pipe wrench.
http://www.grainger.com/Grainger/RID...e-Wrench-1VUV1

Ah. I had never seen one of those before!
Hand Tools Plumbing Tools Plumbing Specialty Tools
RIDGID Internal Pipe Wrench, 1-2 In Cap, 4 1/2 L
Internal Pipe Wrench, Capacity 1 To 2 In, Overall Length 4 1/2 In,
Steel With Sliding T Handle and Knurled Jaws,
Jaws Expand By Eccentric Action and Are Reversible For Various Sizes,
Holds Closet Spuds, Bath, Basin and Sink Strainers Through 2 In,
Used To Install or Extract 1 to 2 In Nipples

Nor these:
GENERAL Pipe Wrench Set
Internal Pipe Wrench Set, Pipe Capacity 3/8 to 1 Inch, 4 Pieces,
To Remove Frozen Pipe