Regular fields can be used in text, mtext, or attributes to display object or drawing properties, like the area of a polyline or the date and time a drawing was last plotted. For most fields, it doesn't matter where you put them. Whether they're in a text, mtext, or attribute object, they'll behave the same way. But there's a special category of fields, called "block placeholders", that can only be used inside attributes inside the block editor. The reason for this is that they're pulling properties from the block instance itself, and these properties can change as actions and parameters are adjusted. All blocks can make use of the following properties: Block Unit Color Layer Linetype Linetype Scale Lineweight Material Name Object Name Plot Style Position Rotation Scale X Scale Y Scale Z Unit Factor In addition, the dynamic properties unique to that block definition will also appear in that list. For example, here are the available block placeholder fields for a fluorescent light dynamic block: And for a steel beam section: (For my non-structural readers, those abbreviations are for Flange Width (FW), Flange Thickness (Tf), and Web Thickness (Tw).)Let's say I decide to use the Size variable in my new attribute. When I close the Block Editor and save changes, I can see the size of each beam next to the beam itself. (After running Synchronize Attributes, of course.)

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