There was/is a pole method used in certain euro-land units. Not sure it is what you are thinking of, but when they do their method it is a very quick way of getting a man onto an external 1st, or 2nd floor surface, or outside a window.
I have tried to find a reference to the 5.5's use as bunker busters in Burma, but can't find one.
I read about their use in John Masters' books, "Bugle and a Tiger" and "Road past Mandalay"
Both books are excellent, giving details of the life of an officer in the Indian Army, mostly the Gurkhas, from 1937 to 1946.