The concept of a line assists the person in completing a goal. The activity is a general aim or purpose. The standard of performance varies within ACL 4 Low. In ACL 4.0 the standard is drawn from the person's long-term memory. The sample maybe referred to only once in the beginning or when they are prompted. In ACL 4.2, only one linear information is used at a time usually either the vertical or horizontal line at a time. In ACL 4.4, the person can use linear information of horizontal and vertical information at a time. The person needs to constantly match to the sample.