A block reference can contain other blocks nested within it. For example, you can insert a drawing of a mechanical assembly that contains a housing, a bracket, and fasteners, with each fastener composed of a bolt, washer, and nut. The only restriction on nested blocks is that you cannot insert or create blocks that reference themselves.
Sometimes a nested block contains objects that are on layer 0 or that have color, linetype, and lineweight specified with BYBLOCK. The properties of these objects are determined by the block that contains them in the nested structure.
Although block nesting can be useful, floating layers, colors, linetypes, and lineweights can make nesting complicated if they aren’t used correctly. To minimize confusion, follow these guidelines:
- If all instances of a particular block need the same layer, color, linetype, and lineweight properties, assign properties individually to all objects in the block (including any nested blocks).
- To control the color, linetype, and lineweight of each block instance by using the properties of the layer on which you insert it, draw each of the block’s objects (including any nested blocks) on layer 0 with all properties set to BYLAYER.
- To control the color, linetype, and lineweight of each block instance using the current properties, draw each of its objects (including any nested blocks) with color, linetype, and lineweight set to BYBLOCK. Before creating a block, you can change the layer, color, linetype and lineweight of its constituent objects with PROPERTIES.