CONVENTIONAL USES FOR LINETYPES:

Dashed lines are often used to indicate items above the plan cut or in front of the section cut, or objects below or beyond a visible surface.

A “center” linetype (a repeated pattern of single long dash and single short dash) is usually used to indicate gridlines or center lines of objects or spaces.

Specialty linetypes are often used by various engineering disciplines to indicate utility routes; such linetypes often consist of a dashed or broken line annotated with the service description.