when a person has a very square, broad face and a very wide mouth they are said to have a letter box face. This is because their square shaped head looks like a door, and their mouth would be the letter box. If a man has a large beard,aswell as a letter box face, they would also have a welcome mat.
"his mouth is so wide and his face is so square that he looks a bit like a letter box." said jill.
"yeah he has a letter box face." said mollie
"and he also has a long beard" said jill
" thats his welcome mat" said mollie