A mask block is a two-dimensional (2D) block that covers, or “masks,” part of the graphic display of an AEC object in a plan view. You can use mask blocks to clean up or correct objects in your drawings or to create custom 2D shapes from predefined drawing objects, such as walls or grids.
For example, attach a light fixture as a mask block to a ceiling grid in a plan view. If the light fixture is bigger than one or more of the ceiling grid bays, the light fixture masks, or covers, the ceiling grid lines that would visibly pass through the light fixture if it had been defined as a regular AutoCAD block.
Before you can begin to mask objects in your plan view drawings, you must have an existing mask block or a mask block definition created in your drawing. You can find predefined mask blocks on the Drafting tool palette and in the AutoCAD Architecture 2024 toolset Stock Tool catalog. You can also create a mask block with the AEC Content Wizard.
After you have selected a mask block, add it to your drawing in plan view. Adding the mask block to your drawing is like adding a regular AutoCAD block: specify an insertion point or scale factors and a rotation angle. The mask block and the object that you want to mask must be coplanar; that is, for the mask object to cover the other object, they must be on the same plane.
After you insert a mask block in your drawing, attach the objects to be masked. The mask block clips the graphics of the objects that you are masking when the objects regenerate themselves in a plan view. Only the objects that you attach to the mask block are clipped. The masked objects are plotted as you see them on your screen.
If you change your drawing from a 2D view to a three-dimensional (3D) view, the mask block is still displayed, but it no longer masks the objects that are attached to it. You can detach the mask block from the objects at any time. You can also import and export mask block definitions. If you create a mask block definition that you decide not to use in your drawings, you can purge it.