In a conversion to HTML, a <hint> to an <exercise> renders nicely in a knowl, right below the exercise statement. For a conversion to LaTeX/PDF/print, you might wish to display a hint, visibly, as part of the exercise, or you may wish to park the hint in a Hints to Exercises division in the back matter. To control visibility of the components of exercises (and projects) there are twenty switches you can use. See Section 26.4 for more.
