Select, Mask opens the Mask panel, which gives more detailed control over the pick mask than the Mask toolbar implementation provides.
The Mask panel provides finer control over pick masks than available on the toolbar.
Other than Database Boundaries and Groups, all mask options are in frames which are closed by default. Simply click the check box for that entity type to expand the frame. Entity type options that are checked in the Mask panel can be selected, while entity type options that are not checked cannot be selected.
Check open the frame to see options for a given entity type.
Selecting a specific Type, for instance of domains, will expand the masking options further to allow even more selection control. For blocks, selecting a Type also provides additional masking options.
Selecting a Type of domain expands the masking options further.
Note there is some interaction between the Mask panel and the Mask toolbar. If some of the entities in a basic entity type are checked and some are not, the corresponding toolbar button will appear with a filled square rather than a check mark. This indicates that the particular entity type is neither all on nor all off. For instance, if unstructured blocks are checked on and structured blocks are checked off in the Mask panel, the check box next to the block symbol in the Mask toolbar will become filled as shown below.
The filled check box next to the block symbol in the Mask toolbar shows that some types of blocks are pickable but others are not.
Likewise, Mask toolbar actions will affect the state of the check boxes in the Mask panel. In the example above, if the check box next to the block symbol is checked, all the block types will become selectable and the corresponding check boxes in the Mask panel will have check marks in them.
Similar interaction also occurs between the Mask toolbar and the List. That is, if the check box next to the block symbol is unchecked, none of the blocks will be selectable in the List. Note that when the Mask is checked on for database boundaries, they can only be seen and selected in the Display window and are not available in the List panel.