masking vs masking piece

masking and masking piece both are nouns.

Word	Noun	Adjective	Verb	Adverb
masking	Yes	No	No	No
masking piece	Yes	No	No	No

As nouns, masking and masking piece are synonyms defined as:

masking and masking piece: scenery used to block the audience's view of parts of the stage that should not be seen

masking (noun)	masking piece (noun)
the act of concealing the existence of something by obstructing the view of it	scenery used to block the audience's view of parts of the stage that should not be seen
scenery used to block the audience's view of parts of the stage that should not be seen
the blocking of one sensation resulting from the presence of another sensation