The time-honored way these work is that the wasp (or hornet, yellowjacket, or fly) is enticed by any sweet liquid to fly up into the jar through the hole in the base. Once inside, the bug will invariably drown. When full, you simply pull out the top stopper and empty the Trap. Hang it from any convenient branch, nail or hook; it requires no maintenance whatsoever, except an occasional look-see and cleaning. Leave outdoors all the time, except if freezing.
These are still made in modern forms today, but ours are exact replicas of an antique Victorian wasp trap which we came across years ago during trip through the Lake District in England - hand made now for us in Mexico by a small, custom glass blowing firm we discovered. They have a great deal of style, and are very decorative as well as functional.
Each is about 5-1/2" tall and 4" wide, and each comes with its wire hook and a genuine cork stopper. Some variation in size should be expected.