Shulachan Aruch (OC 135:10) holds, and Rama (there) seems to also hold, that if a kohen (or levi, m.m.) is called as acharon then the gabai should say "af al pi shehu kohen". The purpose of this is to ...
Following kedusha during mussaf on a day when there is birchas kohanim (duchening), the Leviyim and Kohanim assemble at the sink and a Levi washes each Kohen's hands. What procedure of hand-washing ...