A template is a device used by sanctioning body officials to check the body shape and height of racing vehicles.
[1] The template is used to check that teams have manufactured the sheet metal used in the vehicle bodies to within tight tolerances (up to thousandths of an inch).
Before the change, there were different templates applied to each car model to make sure it resembled the factory version of the car.
[3] The differing templates frequently caused NASCAR to adjust the templates to ensure that all makes of cars were as aerodynamically equal as possible (called "parity").
All Car of Tomorrow models utilize the same templates, since the CoT is designed to not resemble a specific street car.