A padeye is a metal fitting, usually U-shaped, whose threaded ends can accept nuts. NauticExpo offers a wide variety of padeyes: semicircular, articulated, shroud, etc.
A padeye is used to anchor or hold a line, a cable, etc.
Padeyes are usually made of corrosion-resistant metals, such as stainless steel, galvanized iron, etc. While they come in various configurations, most are U-shaped with threaded ends to hold nuts.
Choice will depend on intended use, size, configuration, material, etc.