Metal curtain hooks come in many shapes and sizes and perform many different tasks. They are usually made of brass or zinc plated. By virtue of the fact that metal is very strong, they should used for heavy curtains and always be used in sunny window positions as plastic curtain hooks will become brittle after prolonged periods in the sun.
Some types of metal curtain hooks are also called pin hooks. They come in several sizes and are used for curtains that do not have any heading tape such as pinch pleat and goblet heading curtains. They have a sharp end hence the name pin hook at one end and the other end doubles back on itself to become the hook. They pin into the heading and fix the curtain to the track or glider.
Box pleat or pinch pleat hooks are also metal and have two or three prongs rising above the hook which poke into the special heading tape to reinforce the pinches into groups before attaching the curtain heading onto the rings or gliders.