-Before we tackle this, let us remember that object properties
-are grouped in what are called @emph{interfaces} -- see
-@ref{Properties found in interfaces}. This is simply to
-group together those properties that are commonly required
-together -- if one of them is required for an object, so are
-the others. Some objects then need the properties in some
-interfaces, others need them from other interfaces. The
-interfaces which contain the properties required by a
-particular grob are listed in the IR at the bottom of the
-page describing that grob, and those properties may be
-viewed by looking at those interfaces.
-
-We explained how to find information about grobs in
-@ref{Properties of layout objects}. Using the same approach,
-we go to the IR to find the layout object which prints
-bar lines. Going via @emph{Backend} and @emph{All layout objects}
-we find there
-is a layout object called @code{BarLine}. Its properties include
-two that control its visibility: @code{break-visibility} and
-@code{stencil}. Barline also supports a number of interfaces,
-including the @code{grob-interface}, where we find the
-@code{transparent} and the @code{color} properties. All
-of these can affect the visibility of bar lines (and, of course,
-by extension, many other layout objects too.) Let's consider
-each of these in turn.
+Before we tackle this, let us remember that object properties are
+grouped in what are called @emph{interfaces} -- see @ref{Properties
+found in interfaces}. This is simply to group together those
+properties that may be used together to tweak a graphical object -- if
+one of them is allowed for an object, so are the others. Some objects
+then use the properties in some interfaces, others use them from other
+interfaces. The interfaces which contain the properties used by a
+particular grob are listed in the IR at the bottom of the page
+describing that grob, and those properties may be viewed by looking at
+those interfaces.
+
+We explained how to find information about grobs in @ref{Properties of
+layout objects}. Using the same approach, we go to the IR to find the
+layout object which prints bar lines. Going via @emph{Backend} and
+@emph{All layout objects} we find there is a layout object called
+@code{BarLine}. Its properties include two that control its
+visibility: @code{break-visibility} and @code{stencil}. Barline also
+supports a number of interfaces, including the @code{grob-interface},
+where we find the @code{transparent} and the @code{color} properties.
+All of these can affect the visibility of bar lines (and, of course,
+by extension, many other layout objects too.) Let's consider each of
+these in turn.