A question I find myself answering a fair amount is “Who put the cat in there?!”; more Revit related, I get asked “what the heck does that little ‘3D’ by my grid bubble mean?” a lot.
The “3D/2D” button by gridline heads is often a source of confusion, partially, I think, because of the nomenclature they used for the system. It’s a good system, but really has nothing to do with the traditional definition of 3D and 2D. Semantics has often been an issue in Revit (looking at you, “Save to Central”) that often the team does a good job of fixing (looking at you, “Synchronize with Central”). So far, the 3D/2D toggle is not one of them.
So, if you click a gridline, you will see a tiny “3D” up by the grid bubble. The terminology is flawed. Essentially, what the “3D” means is that this grid bubble position is shared throughout the project, and if you move it, you will move it in other views as well, and wherever you put it, that’s where it will show up in any view where that grid bubble is marked “3D”, or just outside the annotation region, depending on which is shorter.
When you click it, it changes to “2D”. This basically means “View Specific”. So, if you move the grid end now, it won’t affect any other views. This view is it. You will see a ghost grip where the “3D” of the gridlines is. Dragging the head back to this will reset it to “3D”.
Now, let’s say you click the 2D on for some of your grid bubbles and you move them and you really like the positioning in this view, so you want to copy it to other views. That’s where the “Propagate Extents” button comes in to play.
Select the gridlines you want to copy and click “Propagate Extents”. You will be prompted with a list of parallel views. Select the views you want to copy to and then the gridlines position settings will be copied onto those views. It’s a one-time thing for the “2D” gridlines, so if you were to tweak the position after propagating, you would need to re-propagate to get those new settings pushed over.
Do I have a solution for the 3D/2D terminology fiasco? Not really. The only better icon I could think of would be a little chain to replace the current “3D” and a broken chain or chain with a slash through for “2D”… for “linked” and “unlinked”, get it? Is it better? Who knows. Will it ever change? Who knows that either. But hopefully the above clears it up.