G'day Naveen and BW,
Yes, I was likewise bamboozled by the term.
But, there is some info re flange bearing frogs at Wikileaks.
https://www.google.com/url?sa=t&rct=...rAs7hZzocW-pmE
And if that link works, a PDF file apparently details the H type crossing.
I haven't downloaded the PDF, so don't know exactly what it details.
Steve.