Sign is related to Wall. you are likely to find Shelf in/at/on Wall. Shelf is related to Rack. Carrier is a type of Rack. 
Yard can be used for Storage. Yard is related to Measurement. 
Sign <--RelatedTo--> Wall <--AtLocation-- Shelf <--RelatedTo--> Rack <--IsA-- Carrier 
Storage <--UsedFor-- Yard <--RelatedTo--> Measurement 