The basics of blocks are the same in Rhino 4 and 5. However, Rhino 5 offers additional features and commands that you will find here.
> Summary: Blocks provide a way of managing repeated objects in a file.
When you make a block in Rhino from geometry in the current file with the Block command, Rhino replaces the geometry you selected with a block instance. It saves the block definition (the geometry you selected to define the block) in the file. You can insert as many instances of this definition as needed with the Insert command. Existing block definitions available for inserting are on a drop down-list in the Insert dialog box.
If you insert another 3dm file as a block instance, a similar thing happens. The block definition is sucked into the current file and saved with it. What you see on screen is an instance of geometry. The difference, of course, is that the definition refers back to the external file and can be updated as well as any instances that are placed if the external file is changed. This is done via BlockManager.
In both cases, there need not be any actual instances placed in the file for the block definition to exist in the file. This is why you sometimes have trouble deleting layers. If a block definition uses the layer, you cannot delete it. This can happen when all instances of a block have been deleted. Use the Purge command to get rid of unused block definitions.
To update all block instances of a particular block in the file, you need to redefine the block definition. Explode a block instance.
Redefine the Block in Rhino 4:
Redefine the block in Rhino 5:
In Rhino 5 you can use the BlockEdit command.
Block definitions that are from external files can be updated by editing and saving the external file then updating the definition in BlockManager The definition looks at the absolute path, by the way, so you cannot move external files used in block definitions and have the update work, but the current definition does not care if the original source file moved- the current definition is in the current file.
Notes about layers: