The term 'HOLDS FIRMLY' can be summarized by two crossword solutions: RIVETS (6 letters) and GRIPS (5 letters). RIVETS are fasteners used to join two or more pieces of material together. They are usually made of metal and have a cylindrical shape with a head on one end. The other end is inserted into a hole in the material and then the head is hammered down, creating a tight hold. Grips are also used to hold objects firmly in place. They are usually made of rubber or plastic and have a textured surface that helps them grip onto the object.