Normally Marker Symbols are output as inserted Block entities with a single name, e.g. ‘_DOT’ for the predefined ‘Solid Circle’ marker.
However you can also apply names to markers, such that each name will correspond to a particular symbol. It is useful to do this where you already have your own BLOCK entity definitions to represent certain types of features, defined in AutoCAD or another CAD program. In AutoCAD when a DWG file is inserted into a ‘prototype’ drawing which already contains identically named BLOCKS to those in the inserted drawing, it will use the ‘prototype’ definitions in preference to the inserted definitions.
As an example say that a key field called ‘FNODE’ has values such as ‘AIRFIELD’, ‘RESTAREA’, ‘TRAILERPK’. Selecting ‘FNODE’ as the Key Field for producing marker Block Names will result in inserted block entities called ‘AIRFIELD’, ‘RESTAREA’, ‘TRAILERPK’. In this example we will say that ‘Solid Circle’ was selected as the Marker. The resultant file when opened as a new drawing would result in the drawing at left in the following illustration (the ‘AIRFIELD’, etc. in brackets would not actually display in the drawing.) On the other hand, the ‘AIRFIELD’, ‘RESTAREA’, ‘TRAILERPK’ may also be BLOCK entities that have already been defined and are being used as the standard graphic representations of the respective items. In that case inserting the translated drawing into a prototype drawing containing these BLOCK definitions would result in a replacement of the ‘solid circle’ definitions with the matching named graphic definitions, as displayed in the right of the illustration below. If any named definitions did not exist they would simply be displayed as ‘solid circle’.