You may have noticed layers named 0, ByLayer, and ByBlock in the Layer Properties dialog box without realizing that they have special uses. At the same time, you may not be aware of the layers that should be used to define blocks. If you are like me, then most of the time we just select several objects that happen to be on different layers with a variety of properties, and then create a block that sometimes ends up with annoying problems. Today, I would like to share with you the result of my study on the relationship between these issues - blocks, layers, and properties -- in ZWCAD 2011.

The layers and properties with which we define blocks definitely have an effect on whether we can change the layers and/or properties individually later when we insert the blocks in drawings. The following table summarizes the results of my studies:

A. Definition Layer: Any layer (except 0)

• Set color, linetype, lineweight ByLayer

a) Block keeps the properties of the definition layer. You cannot change the block's properties unless changing the definition layer's properties.

b) The layer is created, if necessary, when inserted into other drawings.

c) If the drawing already has a layer of the same name, the block will take on the properties of this layer.

• Set color, linetype, lineweight ByBlock

a) Block takes on the properties of the current layer.

b) You can change the block's properties as you need.

c) The definition layer is created, if necessary, when inserted into other drawings.

B. Definition Layer: Layer 0

• Set color, linetype, lineweight ByLayer

a) Block takes on the properties of the current layer.

b) You cannot change the block's properties, except by changing the inserted layer's properties.

c) No new layers are created when inserted into other drawings.

• Set color, linetype, lineweight ByBlock

a) Block takes on the properties of the current layer, and you can change the properties as you need.

b) No new layers are created when inserted into other drawings.

C. Definition Layer: Any layer (including 0)

• Set color, linetype, lineweight specific settings: such as color in red

a) Block keeps the properties that were set during definition.

b) The definition layer is created, if necessary, when inserted into other drawings.

Based on the information listed above, I recommend following actions when creating blocks with ZWCAD:

• To create blocks that will be inserted in more than one layer, create the blocks on layer 0, and set all properties to ByLayer.

• In all other cases, make your decision according to your unique needs.