The Net Scan command is used to "sniff out" and illuminate all tracks, pads, and vias along a signal pathway. Once hilighted, the signal net may be re-named.
To scan a signal net, you must first position the cursor somewhere along the desired signal and then press <left mouse> or <Enter>.
The target line segment is first hilighted, then, recursively, each line segment, pad or via that it is in electrical contact with.