An example of a problem is: bolts are cross-threading in the engine block on the production line.
#Why? - The threads aren't cut cleanly.
#Why? - The cutting tool on the lathe wasn't changed today.
#Why? - The replacement cutting tool bin was empty.
#Why? - The bin's contents had fallen and rolled under the shelves.
#Why? - One of the feet on the shelves has rusted and failed, making the shelves unstable, and when it was jostled, many parts fell on the floor, including the lost cutting tools.

In this example,