Obscure or “hide” a region of linework in relation to other linework. Use this feature when you want to indicate that one entity extends behind or beneath another entity that is displayed in the foreground. The obscured linework is placed on the layer specified by the Hidden layer key.
The obscured region is delineated with a dashed line. You can select it (or its component segments) separately from the linework it was part of before being obscured.
Obscuring linework with a block