*SetFieldLength() - symmetric field pair
Sets the length properties of a symmetric field pair.
Syntax
*SetFieldLength(field_name, LEFT|RIGHT, length_x, length_y, length_z 
                                      length_rx, length_ry, length_rz)
    Arguments
- field_name
 - The variable name of an existing field pair.
 - LEFT RIGHT
 - If LEFT is specified, the properties are assigned to the left field, and the right field properties are made symmetric to the left field.
 - length_x length_y length_z
 - The field values at length_x, length_y, and length_z, respectively.
 - length_rx length_ry length_rz
 - The field t_x, t_y, and t_z values at length_rx, length_ry, and length_rz, respectively.
 
Context
Comments
Nonlinear properties for stiffness or damping cannot be specified for a symmetric field pair.