Some call them jigging spoons, some call them slabs (not to be confused with the crappie, which some people also call slabs). But whatever you call them, they are an effective addition to your tackle box.
They are a great white bass or striped bass lure. The way I like to use them is on the boat over the side. Typically while drifting, I will drop them over the side until they hit the bottom, then pull them up to a depth just above where the fish seem to be holding at on the fish finder. Dipping that lure up and down above and into the fish seems to be the most effective. White bass, striper and wipers (hybrid white/striper) seem to prefer coming up for a bait rather than going down.
Simply casting out, letting it sink, then reeling in can be a good producer as well. The sheer weight of the slab allows you to cast it much farther than any other lure.
Another successful technique I see used with slabs is the double lure technique. A basic doll fly is tied on about 1-2 feet above your slab spoon. This is jigged in the same way as I mentioned.
Trolling can also be a successful technique with a slab. Whether you use the double lure method or just the slab alone, drop it into the water as you drift roughly 1 mph across the lake. The weight of the slab help keeps it deep.
Experiment with different colors for different types of lighting and water clarity.