How do you make three word compound nouns plural?

Normally, the first Word in a three Word hyphenated compound noun is the main noun. For example for commander-in-chief, the 'in-chief' is the description or title of the commander; as for mother-in-law, the 'in-law' is the description or title of the person.

When making a three Word hyphenated compound, the main noun is pluralized:

• commanders-in-chief
• mothers-in-law
• ports-of-call
• birds of prey
• jack-in-the-boxes (uh-oh, an exception?)

When you have compound nouns, you also have to think about which part of the Word has multiplied:

• newspaperman, newspapermen
• airline pilot, airline pilots
• manhole cover, manhole covers
• third-grade teacher, third-grade teachers