A Block is a user-defined region of the data base. Objects that are displayed and satisfy the Block criteria will be acted upon by the functions that operate in association with Blocks.

The Block command is available from all task menus and is available in all Plan, Long Section, Cross Section and 3D windows in the LISCAD Surveying and Engineering Environment. In LISCAD Lite the Block command is only available from the Plan window.

Blocks can be defined either by Freehand or by Polygon, although Polygon is not available in the 3D View.

The Block types supported in the various view types are as follows:

Blocks are always de-activated after they have been used by a function. To re-activate or de-activate a Block when not in the 3D View, use the Toggle Block Tool. In the 3D View, this command is disabled.

In the 3D View, Block behaviour differs from the other views. In 3D View, a block cannot be defined until a dialog that can use a block is active. Then, when a block is defined, objects that fall within the criteria of the defined block are highlighted and ready for the function to be performed upon them. Once that function has been performed, the selection is not saved, so the block can not be toggled. (This is because unlike in a Plan View, where the concept of a camera does not exist, the area defined by the block can alter when the properties of the active camera change, and therefore can become ambiguous).

 In summary, a block cannot be defined in 3D unless there is a dialog open to act on points, lines, triangles or scan data.