Do you know what the rows of "small serrations" along the edges of a PCB board are for? Many people mistake them for leftover marks from cutting, but they are actually called discharge teeth. Their function is to help the PCB safely release excess static electricity during production and use, preventing damage to sensitive components.
 
Don’t underestimate this small design—it often determines whether a PCB can work stably and durably. Next time you see them, don’t think of them as "notches" anymore; they are the "protective shield" of the circuit board.