Use a locative classifier
Classifier is a pronoun-like linguistic symbol that represents a class or group of referents. In ASL, a noun should be signed first before using its classifier to refer to it until a subject or noun is changed.
Locative classifier (LCL)
Below shows an example of using a pathline of locative classifier. Index finger is the common handshape for a pathline in a verb predicate.
Gloss: ball thrown cl-pathline[medium]