Must is related to Sign. Sign is a synonym of Trail. Trail is related to Slope. Slope is related to Decent. 
Product is related to Material. Plastic is a type of Material. Plastic is related to Wrap. 
Must <--RelatedTo--> Sign <--Synonym--> Trail <--RelatedTo--> Slope <--RelatedTo--> Decent 
Product <--RelatedTo--> Material <--IsA-- Plastic <--RelatedTo--> Wrap 