There’s a lab scene in the latest Batman movie, The Dark Knight, where Bruce Wayne tells Alfred, the butler, “There’s the thumbprint he left when he pushed the round in the clip.” Bruce Wayne, like many handgun owners, was using the term “clip” to refer to a pistol’s magazine. Although both a magazine and a clip retain ammo in a ready-to-use condition, they are quite different in appearance and application.

Magazines are basically rectangular tubes that vary in length to fit inside a pistol’s grip, and they are used to store and load ammo into all semi-auto pistols. Magazines also vary in width, being either single- or double-column, and, while the latter hold more cartridges, they can also make the grip thicker. Some magazines are made entirely of metal while others are a composite of metal and polymer. Magazines fully enclose the ammo they contain, helping to protect it from damage and dirt.

Semi-auto pistols are designed to work with an extractor that hooks into a groove at the base of the cartridge as part of the ejection cycle. Almost exclusively, semi-autos use cartridges of a “rimless” design. Revolvers, on the other hand, require a rimmed cartridge so that the cylinder’s ejector, which sits under the rim of each cartridge, has something to push against to expel the spent cases from the chambers in the cylinder.

However, some revolvers are designed to shoot the rimless 9mm or .45 ACP cartridges, both developed for semi-autos. Since the heads of these cartridge cases don’t have projecting rims, manufacturers provide “clips,” usually made of thin metal, that snap into the groove of the case. The clip, holding the rounds as a unit, is dropped over the ejector as the cartridges slip into the cylinder holes. Since a clip holds enough cartridges to fully load the revolver in one step, they also function like magazines by enabling fast reloads. But clips are easier to damage and lose than are magazines. They tend to be bulkier when carried on the belt, and carriers for them are harder to find.

One manufacturer is working on a revolver that can retain and eject semiauto cartridges without the use of clips. Until that gun is available, the only way revolver shooters can benefit from the ballistics or the cost efficiencies of semiauto cartridges is by the use of clips.

So, when it comes to handguns, just remember that all semi-autos use magazines, and only a few revolvers use clips. Hollywood still may not know the difference, but you do.