In addition to the guidance found here in the Editorial Guide, please see information on the use of templates at SNOMED CT Modeling Templates and Description Patterns.
Templates are created by authors in an attempt to standardize the modeling, naming, case significance, etc. of certain subhierarchies of the terminology, though it is recognized that not every concept may conform to a prescribed pattern. The modeling approach may be difficult to apply in all cases, but domain-specific templates are being developed to ensure modeling consistency and accuracy.
When to create a template
No template is necessary if less than 50 concepts are affected. In cases of small numbers, check if existing templates can be generalized and/or look to add elements as optional rather than mandatory.