Waste was identified at multiple levels, for example, overproduction of a particular part was seen as waste for two reasons. Firstly, space was needed to stockpile the part until it could be used. This cost money not only for storing it but also took up floor space that could be used for production. Secondly, sometimes problems in the manufactured parts weren't found until they were combined with other parts and put to use further down the production line. If a problem were discovered that required the entire batch to be re-machined or re-manufactured, this would add significant time and money.