In the Label Style Composer dialog box, click the Layout tab.
Select a component from the Component Name list.
Click the Value column for Lineweight, and then click .
In the Select Lineweight dialog box, select a lineweight, or select one of the following options:
ByLayer. Labels obtain their lineweight from the label style’s layer (defined on the General tab of the Label Style Composer).
ByBlock. Labels obtain their lineweight from the parent object’s AutoCAD properties. The object is first examined for any property overrides. If none are found, then the lineweight property of the object layer is used.