When used on a verb of motion, the prefix за- has the following meanings: stop in (at somebody's place) (used with к + Dat.) stop by for (to pick somebody up) (used with за + Inst.)
Ї зашлђ к немџ.	I stopped in at his place.
Ї зайдџ за вђми в пїть.	I'll stop by for you (pick you up) at five.