masking

Noun

• 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
  • he studied auditory masking by pure tones
    

• the act of concealing the existence of something by obstructing the view of it
  • the cover concealed their guns from enemy aircraft
    

Related words

• Synonyms: 
  masking piece , cover , covering , screening