A panel nut is very thin nut

Nut (hardware)

A nut is a type of hardware fastener with a threaded hole. Nuts are almost always used opposite a mating bolt to fasten a stack of parts together. The two partners are kept together by a combination of their threads' friction, a slight stretch of the bolt, and compression of the parts...

 with a relatively large hole commonly used to mount threaded

Screw thread

A screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force. A screw thread is a ridge wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread and the latter called a tapered thread...

 electrical

Electricity

Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...

 switch

Switch

In electronics, a switch is an electrical component that can break an electrical circuit, interrupting the current or diverting it from one conductor to another....

es.
These are often used where light duty precision fasteners are needed. They have width close to the diameter of the fastener they secure. These usually have low thread count. They are of two types hexagonal panel nut and knurled round panel nut.
Applications : Panel nuts are used in potentiometer control, light weight lock nut, switch hardware.
Material :Brass, stainless steel, aluminium are the materials commonly used for this nut. Panel Nut Wrench: It is a double ended tube socket type tool for removing nuts.