expansion wedge anchor

20mm chipboard screws typically feature a coarse thread, which allows for quick penetration into the board without causing excessive strain on the material. Their length, 20 millimeters, is ideal for most applications, providing ample depth for secure fixing without protruding through the other side. The sharp point at the tip ensures easy entry into the board, while the Phillips or Pozidriv head offers a secure grip for the driver bit, reducing the chances of slippage during installation.

...

A wafer head self-drilling screw, as the name suggests, is designed with a flat, thin, and round head that closely resembles a wafer. This design not only ensures a flush finish but also provides a broad surface area, distributing load evenly and reducing the chances of material splitting. The unique feature that sets it apart from conventional screws is its self-drilling capability. Equipped with a sharp point and specialized threads, these screws can penetrate through metal, wood, or plastic without the need for a pre-drilled hole, saving time and effort.

...