Matching and correcting are the verbs that separate ACL 4.0 from 4.2. Within ACL 4.2, matching or correcting are limited to one striking feature at a time. There are five striking features: color, shape, size, number of items (up to four) and linear information. The sample might contain any amount of them but the person will only match one. One at a time might string out to two or three matches but during the process the person is only thinking about one at a time.