A double hane[1] (Japanese: nidan-bane), aka two-step hane is - as the name already suggests - two hanes played in succession. It is a response to White's hane-kaeshi at . Usually it is quite a powerful play, if the local situation allows it.
[1]
Bill: After looking in vain for a double hane on the Stanley 3-3 Double Hane page, I came here. I believe that the proper term in English is two-step hane. Double hane is ambiguous. Just to make sure I was not out of touch, I looked it up in the 2001 edition of the Go Player's Almanac. There is no entry for double hane. There is none for two-step hane either, but nidanbane is defined as a two-step hane. Is there an example of double hane in the English go literature?
Anonymous: IIRC, the book All About Thickness (English translation) lists a proverb: "Learn the double hane and you are nearly shodan."
Another Anonymous: IIRC, James Davies uses the term "double hane" in his books, too. Also, googling for "double hane" (with quotes) yields lots of hits.
Bill: Thanks for the refs. :-) If Davies uses double hane in his books, I am surprised it does not appear in the Go Player's Almanac, since he was a major contributor to it. I see that van Zeijst uses the term, and withdraw my objection. :-)
Robert Pauli: Anyway, with what can it be confused, Bill?
Bill: Playing hane from two sides, for instance. Like so: