Constant is related to Stable. Stable is related to Barn. Barn is related to Straw. Straw is related to Pipe. 
Curtain can be used for Blind. you are likely to find Curtain in/at/on Opera. 
Constant <--RelatedTo--> Stable <--RelatedTo--> Barn <--RelatedTo--> Straw <--RelatedTo--> Pipe 
Blind <--UsedFor-- Curtain --AtLocation--> Opera 