-@samp{on} and @samp{off} or @samp{1} and @samp{0}. A fancier kind of
-Boolean allowed in some cases is the @dfn{lockable Boolean}, which may
-be set to @samp{on}, @samp{off}, @samp{always}, or @samp{never}. If an
-option is set to @samp{always} or @samp{never}, that value will be
-locked in for the duration of the Wget invocation---command-line options
-will not override.