Hallway is related to Main. Main is related to Important. 
Note is a synonym of Use. Use is a synonym of Benefit. Benefit is the opposite of Obstacle. Obstacle is a synonym of Barrier. 
Hallway <--RelatedTo--> Main <--RelatedTo--> Important 
Note <--Synonym--> Use <--Synonym--> Benefit <--Antonym--> Obstacle <--Synonym--> Barrier 