PCB (printed circuit board) covers are designed to protect PCBs and the components attached to them from damage.
PCB covers are used to protect the component side of a PCB from damage caused by impact or contaminants. They also lend a finished look to your circuit. They usually have perforations in each corner so that they can be attached securely to the board. PCB covers can be used in most circuits, but you might need a certain type for your specific needs.
Choosing a PCB cover comes down to the kind of PCB you want to cover. PCB covers come in different sizes and some feature cut out sections so that they can fit over the PCB while leaving specific sections uncovered for easy access. They can also have an insulating coating in the inside and a conductive outer coating, and may be anti-static to prevent the buildup of static electricity.