The ELEV command sets the default Z value for new objects above or below the XY plane of the current UCS. This value is stored in the ELEVATION system variable.

ELEV controls only new objects; it does not affect existing objects. The elevation
is reset to 0.0 whenever you change the coordinate system to the world coordinate
system (WCS).

The following prompts are displayed.

Specify New Default Elevation

The current elevation is the default Z value for new objects when you specify only X and Y values for a 3D point.

The elevation setting is the same for all viewports regardless of their user coordinate
systems (UCS definitions). New objects are created at the specified Z value relative to the current UCS in the viewport. (Not applicable to AutoCAD LT.)

Specify New Default Thickness

The thickness sets the distance to which a 2D object is extruded above or below its
elevation. A positive value is extruded along the positive Z axis; a negative value is extruded along the negative Z axis.