Methods:
Delete - Allows a custom order field to be deleted based on the order field name. (multiple per call)
DeleteOptions - Allows the ability to delete options of a custom order field based on the custom order field and the interop id of the option. (multiple per call)
Save - Allows the ability to create and update a custom order field based on the order field name. Supports the creation of options of an order field as well.  (multiple per call)
SaveOptions - Allows the ability to create and update an option of a custom order field based on the order field name and the option interop id.  If the interop id exists, the option will be updated. (multiple per call)

WSDL URL: http://www.four51.com/services/OrderField.asmx