To create a new schematic symbol, device, panel, or plumbing fitting, you must have at least one block to assign to a view of the style.
You can use a simple 2D AutoCAD® block that is displayed the same in all view directions, such as in the view directions of an orthographic symbol. You can also use a Multi-view block (MvBlock) that has a different appearance for each view direction, such as the different views of an isometric symbol. The individual blocks you create are referred to as view blocks.
The number and types of blocks that you need depend on your requirements. For a schematic symbol style, typically you can create one 2D block to represent the symbol in a plan view. If you need to create isometric drawings, you can use this block to generate additional blocks for the 12 isometric views that represent the 12 isometric view directions and orientations.
For other types of style-based content, you need to create the 2D and 3D blocks required to represent the object in plan views and in model views. For example, a plumbing fitting style might require only a 2D block to represent the fitting in a plan view. Similarly, a device style might require a 2D block to symbolically represent the device in a plan view. However, if you need to create sections and elevations that display devices in actual size, the device style will also require a MvBlock for use in a model view (and in other view directions such as Front and Left).
Generally, when you insert style-based content, you want the symbol to inherit the color, linetype, and lineweight properties of the current layer standard. To ensure this, set the color, linetype, and lineweight properties individually for the geometry in each block. Create the geometry on layer 0, and specify BYBLOCK for color, linetype, and lineweight, and an insertion point of 0,0,0. To ensure the correct view block assignment, assign a unique name to each block. Unique names are also helpful for identification.