This is the 5336th most frequent Polish word.
skrzyni
The Polish word "skrzyni" means "of the chest" or "of the box" (genitive singular form of "skrzynia").
Here, 'skrzyni' is used as the form of the noun 'skrzynia', which means 'chest' in Polish, in the dative case, indicating its role as the indirect object of the sentence.
Skrzyni jest wypełniona ciekawymi książkami.
The chest is filled with interesting books.
In this sentence, 'skrzyni' is the locative case of the noun 'skrzynia', specifying the location where the hinges were fixed.
Naprawiłem zawiasy w skrzyni.
I fixed the hinges on the chest.
'Skrzyni' is in the genitive case here, describing the possession or relationship between 'key' and 'chest'.