The term 'two-by-four' is commonly used to refer to a piece of lumber that is two inches thick and four inches wide. This type of lumber is often used in construction and carpentry projects. The crossword solutions for the term 'two-by-four' are EIGHT (5 letters), octet (5 letters), stud (4 letters), and BOARD (5 letters). EIGHT and octet both refer to the number two, which is the thickness of the lumber. Stud and BOARD refer to the width of the lumber, which is four inches.