Surface is related to Wall. Wall is related to Board. 
you are likely to find Leaf in/at/on Roof. Roof is related to Cover. Cover is related to Judge. Approve is a type of Judge. 
Surface <--RelatedTo--> Wall <--RelatedTo--> Board 
Leaf --AtLocation--> Roof <--RelatedTo--> Cover <--RelatedTo--> Judge <--IsA-- Approve 