Razor wire
Razor wire, also known as unclipped razor wire in some parts of the world, is a single strand of razor wire that is used for security on various types of fence systems.
Like barbed wire, razor wire acts as a deterrent and physical barrier because it is sharp; however, unlike barbed wire, razor wire's sharp points are not made by wire but rather by a thin strip of shaped metal that is wrapped around a core wire. At intervals along that metal strip, sharp metal cutouts stand at about 90 degrees to the central wire, and the pointed ends of that metal form the razor part of this type of wire.
Razor wire is available in a variety of finishes and materials, including galvanized steel and stainless steel, and it can be sourced in short, medium, and long barb versions.