Clarity. Your goal is to produce a document that conveys a single meaning the reader can understand easily. An unclear technical document can be dangerous. A carelessly drafted building code, for example, could tempt contractors to use inferior materials or techniques. In addition, an unclear technical document is expensive. Handling a telephone call to a customer$-$support center costs $$510$ for a simple question but about $$2045$ for a more complicated problem and about a third of the calls are the more expensive kind $($Carlaw$,2010).$ Clear technical communication in a products documentation $($its user instructions$)$ can greatly reduce the number and length of such calls.