Oren wrote, on Fri, 18 Jul 2014 11:06:37 -0700:

Use the black handled "steel" (left) on the two black
handled knives (right).

OK. I'm not sure where I got that "steel" (maybe a
garage sale?); but it has the following stamped on
the cylinder near the handle:

"J.A. Henckels, International, Solingen, Germany"

I'll google how to use a "steel".