Porperties in AutoCAD

When AutoCAD prints (plots) a drawing, each object’s appearance is determined by a sequence of property inheritance rules. Understanding these rules helps avoid surprises.

The property hierarchy

Every object has properties such as:

  • Color
  • Linetype
  • Lineweight
  • Transparency
  • Plot style (CTB/STB)
  • Material (3D)

Each property can come from one of three places:

  1. An explicit property assigned to the object (highest priority)
  2. BYBLOCK
  3. BYLAYER (lowest priority)

For each property individually, AutoCAD determines the value using this order.

1. Explicit object properties

If an object has a specific property assigned, that property is always used.

Example:

Layer: WALLS (green)

Object:

  • Color = Red
  • Linetype = Dashed
  • Lineweight = 0.50 mm

When printed:

  • Prints red
  • Prints dashed
  • Prints 0.50 mm

The layer settings are ignored for those properties because the object has explicit overrides.

2. BYLAYER

BYLAYER means:

“Use whatever properties the current layer has.”

Example:

Layer WALLS

  • Color = Green
  • Linetype = Continuous
  • Lineweight = 0.35 mm

Object

  • Color = BYLAYER
  • Linetype = BYLAYER
  • Lineweight = BYLAYER

Result

The object prints

  • Green
  • Continuous
  • 0.35 mm

If the layer changes later, every BYLAYER object updates automatically.

3. BYBLOCK

BYBLOCK is only meaningful when an object is inside a block definition.

Example

Block contains

Circle

  • Color = BYBLOCK

Text

  • Color = Red

When inserted

Block reference

  • Color = Blue

Result

Circle becomes Blue

Text remains Red

Layer 0 and blocks

Professional block libraries nearly always use

  • Layer 0
  • BYLAYER properties

Why?

When inserted on Layer ELECTRICAL

everything automatically becomes part of the ELECTRICAL layer.

If inserted on Layer PLUMBING

the same block automatically behaves like a plumbing object.

This is why Layer 0 exists.

Printing with a CTB file

Suppose your CTB contains

Object ColorPrinted Lineweight
Red0.50 mm
Yellow0.35 mm
Green0.25 mm
Cyan0.18 mm
Blue0.13 mm
White0.09 mm

Suppose

Layer WALLS

Color = Green

An object

Color = BYLAYER

Result

The object becomes Green

The CTB sees Green

It prints 0.25 mm.

Now another object

Color = Red

Although the layer is Green

the object prints as

  • Red
  • 0.50 mm

because explicit object colour overrides the layer.

The complete inheritance chain

When plotting, AutoCAD determines the effective property in this order:

Object Property
        │
        ▼
Specific property?
        │
     YES│NO
        ▼
Use object value
        │
        ▼
      Finish

NO

BYBLOCK?
        │
     YES│NO
        ▼
Use block reference property
        │
        ▼
      Finish

NO

BYLAYER
        │
        ▼
Use layer property
        │
        ▼
CTB/STB converts that property to the plotted output

Important distinction: CTB vs STB

A CTB (Color-Dependent Plot Style) uses the object’s effective color (after all BYLAYER/BYBLOCK inheritance has been resolved) to determine lineweight, screening, grayscale, and similar print characteristics.

An STB (Named Plot Style) uses the object’s assigned plot style name instead of its color. In STB drawings, color can be used purely for drafting convenience without affecting how the object prints.

Best practice

For most 2D drafting, a simple and reliable standard is:

  • Draw geometry on the correct layer.
  • Leave object properties set to BYLAYER.
  • Create blocks on Layer 0 with properties set to BYLAYER.
  • Let the layer control colour, linetype, and lineweight.
  • Let the CTB (or STB) control the final printed appearance.

This approach minimizes manual overrides, keeps drawings consistent, and makes global changes much easier. Explicit object properties and BYBLOCK should generally be used only when there is a specific reason to override the normal layer-based behaviour.

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