In more recent years, temples were provided with a large outer gate accompanied by side gates on the left and right sides, and later, temples came to have a large outer gate only; however, it is assumed that such a large outer gate remained to be called Sanmon.
時代が下ると左右に脇門が付属する大門の形となり、さらに大門のみとなったが、三門の呼び方は残ったとされる。