Sentence 1: Bob's bought a trailer that had a shingle roof. 
 Sentence 3: Bob checked his insurance policy to see if it was covered 
 Sentence 4:  The insurance replaced the shingle roof with a metal one 
 Sentence 5:  Bob's happy the rain doesn't leak into his house any more 
 Option 1: When it was windy the shingles flew off. 
 Option 2: When it rained the roof would leak pretty badly.