AutoCAD Mechanical ships with 31 layer definitions, which have been assigned to different objects by default. The names of these layers begin with “AM_”, followed by a number or a phrase as described below.
Working layers: Layers AM_0 through AM_12 . Almost all geometry is created on working layers.
Standard part layers: Layers AM_0N through AM_12N. AutoCAD Mechanical commands create standard parts and features on these layers.
Special layers: AM_BOR (used for drawing borders), AM_PAREF (used for part references), AM_CL (used for construction lines), AM_VIEW (used for viewports), and AM_INV (used for invisible lines).