Park is related to Space. Space is a synonym of Blank. 
Used is related to Bed. Bed is related to Structure. Structure is related to Kind. Kind is the opposite of Sharp. 
Park <--RelatedTo--> Space <--Synonym--> Blank 
Used <--RelatedTo--> Bed <--RelatedTo--> Structure <--RelatedTo--> Kind <--Antonym--> Sharp 