Sets the thickness of the trace entity (DXF 39) in drawing units. Thickness is the extrusion length along the normal. A positive value extrudes along the normal. A negative value extrudes opposite from the normal. A zero value defines a trace without thickness. The initial value is zero by default. 

Example of Working with the Trace Object 

Specific Trace Properties 

OdDbTrace::thickness() method

OdDbTrace Methods