A well-designed tool can suggest how it should be used through its shape and arrangement. Visible han guide fami actions wh clear mark indicate impo limits th help peo operate equi without unnec confusion dur ordinary daily tasks. These clues are useful, but they do not replace every kind of instruction. A control may be easy to find while the consequences of using it remain unclear. Designers need to consider what a first-time user is likely to understand. Watching someone attempt a task can reveal difficulties that an experienced operator no longer notices.

Type only the missing letters. Each box is one letter, and the number of boxes matches the letters that are missing.