Disability Inclusion Resources for AmeriCorps Program in Texas Identifying Essential Functions Reprinted with permission from the World Institute on Disability .
Essential functions are the fundamental duties of a service position.
The method used to accomplish the task is not the essential function. Marginal functions are tasks that are performed but are not essential. The ability to operate surveying equipment is an essential function, because this is the reason why the position exists. Since the ability to operate surveying equipment is essential and would, therefore, require the ability to see, an applicant for the position who was blind would not be qualified for the position. Nor would any other applicant, with or without a disability who could not operate surveying equipment.