Create a polygonal area, called a wipeout to mask underlying objects with the current background color.
A wipeout object covers existing objects with a blank area to make room for notes or to mask details. This area is defined by the wipeout frame, which you can turn on for editing, and turn off for plotting. 
Use the WIPEOUT command both for creating a wipeout object, and for controlling whether wipeout frames are displayed or hidden in the drawing.
If a polyline is used to create a wipeout object, the polyline must be closed, contain line segments only, and have zero width.
Using Wipeout Objects on a Layout
You can create wipeout objects on a layout in paper space to mask objects in model space. However, in the Page Setup dialog box, under Print Options, the Print Paperspace Last option must be cleared before you print to ensure that the wipeout object is printed correctly.