This command creates a square cutting plane to cut through an object with theTruncate Object command.  The plane so created is already selected (yellow).  If a face is selected before this command is invoked, the cutting plane will coincide with that face.  Otherwise the adjacent dialog box will appear, allowing you to specify the orientation of the plane to be created.  The azimuth is the compass bearing of the normal to the plane, measured clockwise from the Z axis (arbitrary north).  The incline is the vertical angle the normal makes with the Y axis.  Defaulting both values to zero produces a horizontal plane with its shiny side up that coincides with the groundplane grid.  An incline of 180 degrees results in a horizontal plane with its shiny side down.

The facing of this plane is important to the Truncate Object command.  The cutting plane will remove that part of any object the lies on the shiny side of the plane.  To remove the part below the plane, instead, the facing of the plane must first be reversed with the Reverse Face command.

The cutting plane is a square face that can be moved along its perpendicular with the numeric keypad’s multiply (*) and divide (/) keys (notebook computers have these as ‘function keys’).  Any face can be used as the cutting plane, as long as it is first selected before using the truncate command.   However, the plane created with this command is unattached and can be moved without distorting the rest of the project.  The cutting plane can also be moved with the arrow keys, or rotated with Rotate Mode or the Precise Rotation command.