The Align Plane Settings dialog allows the user to select a plane for the Align Plane digitizing mode. One of the three standard orthogonal planes may be chosen, or a user defined plane entered. In addition, there is a field for the angle tolerance.
Align Plane
The desired plane can be selected from four
choices 
the XY plane, the YZ
plane, the XZ
plane, and the user-defined plane. The first three planes are orthogonal
to each other and correspond to the world X, Y, and Z axes according to
the FaroArm. The user-defined plane is stored
from session to session, and can be modified using the Define
Plane dialog.
Plane Definition Options
The angle tolerance field sets the angle between the digitizer tip and the plane at which the point will be digitized. A tolerance setting of two degrees would create a point at the location where the orientation of the tip became parallel to the align plane within two degrees.