When we change compound nouns into their plural forms, there are some general guidelines that we can follow for each category. That said, it is always wise to consult a dictionary when using these nouns; there are many exceptions to the general rules outlined here!
Noun + AdjectiveIn these cases, both words comprising the compound noun are pluralized.
|la terracotta ... le terrecotte|
la cassaforte ... le casseforti
il caposaldo ... i capisaldi
la cartastraccia ... le cartestracce