What is meant by “buttress”" and by “corner”?

We had come across the term buttress in Nehemiah 3:19, where it referred to a junction in the wall where there was a bend (though not necessarily a sharp bend). That bend gave strength to the wall and so could rightly be called a buttress. The term corner can best be understood as an alternate name for this bend, to distinguish it from the buttress (or bend) below the ascent to the armoury (Nehemiah 3:19). It would be logical that the city’s wall did not follow a precisely straight line, particularly on this eastern side with its precipice.