A blind via hole is a type of via that connects only one or few layers of a printed circuit board (PCB) to another layer and does not extend all the way through the board. They are typically used to connect outer layers of a multi-layer PCB to internal layers, such as power or ground planes, without creating a through-hole that would extend all the way through the board. This can help to save space and reduce the size of the PCB. They are often used in high density and high-speed circuit applications. Additionally, they are also useful in situations where the hole size is limited by the space available on the board, as blind via holes are typically smaller than through-holes.