Each agency will likely have specific documents or letters which have come about as a result of years of experience, and these may vary to some degree from their equivalents used in other agencies.
You can create your own templates via Account Settings > Agency Settings > Templates. and clicking on the Create Template button.
Custom templates added to your template library will be available for selection when creating the relevant letter or document elsewhere in the system, e.g. creating an AST tenancy agreement when a tenant moves into a property.