Plugs are a popular type of hard-bodied fishing lure. They are widely known by a number of other names depending on the country and region. Such names include crankbait, wobbler, minnow, shallow-diver and deep-diver. The term minnow is usually used for long, slender, lures that imitate baitfish, while the term plug is usually used for shorter, deeper-bodied lures which imitate deeper-bodied fish, frogs and other prey. Shallow-diver and deep-diver refer to the diving capabilities of the lure, which depends on the size of the lip and lure buoyancy.

The concept of an attractant tied to the end of a line to entice fish goes back to prehistoric peoples, but the modern concept of the plug lure is attributed to James Heddon, a beekeeper from Dowagiac, Michigan, who was whittling a piece of wood one day in the late 19th century while relaxing alongside a millpond. When he rose to leave, he tossed the carved scrap of wood into the pond, and a large bass struck at it as it wobbled down through the water. Intrigued by this, Heddon began experimenting and perfected a design he dubbed the "Lucky 13" — a plug that is still sold today. By the early 20th century, many companies were in the business of designing and selling plug lures.

The construction of typical plug is:
A solid or hollow body made out of a light weight material such as balsa or plastic, sometimes separated into two pieces joined by a small flexible link to enhance the impression of a fish whipping its tail fin.

A thin sheet metal or plastic lip attached to the front of the body, sometimes adjustable to change the diving ability and wobbling movements of the lure.
Two, or occasionally three, treble hooks.

An eyelet for attaching the fishing line.
Generally, a painted or imprinted color and/or design, to make the plug appear as close as possible to a natural food of the aquatic environment. However, some very effective plugs occasionally have a design or color unlike anything seen in such an environment.

Classic plugs float on the surface or suspend in the water, but will dive under the surface of the water and swim with a side-to-side wobbling movement (hence the alternative name wobbler) upon retrieval. Plastic plugs can dive to either a very shallow depth, due to a small lip, or to a moderately deep depth (i.e. several meters), due to a large lip. The angle of the bib also affects diving depth. Sometimes, plugs are named after their diving ability, e.g. "deep-diver" or "shallow-diver". Plugs can also be designed to hover (neutral buoyancy), sink slowly, or sink rapidly. Some have a small metal ball inside to "rattle" when retrieved.

Other lures are sometimes generically called plugs or wobblers. They come in all different shapes and sizes. These plugs are usually made by small companies and cost around twenty dollars. Each plug has its own action or has none unless you give it one. Wood plugs usually range from between 3/4 oz. and 4 oz. The different plugs come in a few basic categories. There are surface swimmers, subsurface swimmers, needlefish, poppers, pencil poppers, and darters. they all have their own specific place and time to be fished.

Plugs range in size from around an inch (~3 cm) to around 8 inches (~20 cm). Plugs in the 2–3 inch (~5–7 cm) size range are most commonly used however. As a general rule large plugs are used for large fish, and small plugs for small fish. Fishermen casting for very small fish such as crappie will use very small plugs, and anglers fishing for large fish such muskellunge or Murray cod will use extremely large plugs. But trophy-sized fish are occasionally caught on very small plugs, and fingerling perch will sometimes strike — and hook themselves — on a plug as big as they are themselves. Plug fishing is more common in freshwater fishing than saltwater fishing, but it is growing greatly upon East-Coast striper fishermen.

Fishing Technique
Most plugs have their "action" built into them by design, but good fishermen give nuance to the plug's action in many ways, such as varying the speed of the retrieve, occasionally "twitching" the rod tip during retrieve, or even letting the plug stop completely in the water, then resuming retrieve at a very high speed. Plugs are often cast so they land next to places where fish may be hiding, such as a snag pile or an overhanging tree and worked back enticingly. A skilled fisherman can methodically explore many possible hiding places for fish by continually casting and retrieving a plug.

Theoretically, any plug design will catch fish — fish will, out of anger, hunger, territorial protection or simple curiosity, occasionally strike at any small object moving or falling through the water. But some plugs have become famous for their high degree of effectiveness in the hands of a good fisherman, while others come and go from the market quickly when found to have limited success.