When you're out walking and someone has a visible total of four pocket knives on them. Especially the folding knife types. Swastika stalking is called that because four folding knives folds up halfway between open and closed to make a actual swastika double Cross, it implies but doesn't require the swastika stalker to be expecting their knives are going to get full very dull if they've brought four knives. Usually a knife is carried by itself or in pairs depending on the manufacturing process. The swastika stalker is essentially bringing the world's simplest p.d.w.
"Look over there next to the kegs over there, that guys swastika stalking. Let's go I think that guy could single handedly take the city if they walk quietly. I mean it lets go"