The term 'CERTAIN LOCKS' can be solved by two crossword solutions: YALES (5 letters) and TRESSES (7 letters). Yales are locks that are used in door hardware, typically found on residential doors. They are named after Linus Yale, Jr., who invented them in the 1840s. TRESSES are a type of lock that is made up of several strands of hair or other material that are intertwined together. They are often used as a decorative element in hairstyles and clothing.