Your glasses sit on your face every day, but would you be able to explain to someone what all their different parts are? It’s good to know a little about what you’re wearing, so here’s a quick rundown of the parts that make up your glasses or sunglasses. This can be useful if you have a problem that needs repair and need to describe it to an optician.

The Lenses

Probably the most obvious and important parts of eyeglasses are the lenses. Specially ground spectacle lenses are convex on the front and concave at the rear. Coatings for lenses include mirrored, tinted and polarized. They can be enhanced for specific duties such as playing sports, using computer screens regularly or driving at night without suffering from glare.

The Lens Rims

The lenses are surrounded by the lens rims (or at least, they are unless you own a pair of rimless spectacles.) The lenses fit into the rims in a small groove and are held in place by that groove.

The Frames

You’ll find frames made of some kind of metal or plastic. Metals used include nickel, stainless steel, aluminum and titanium. Titanium is expensive but ideal, as it is strong, light, corrosion-resistant and hypo-allergenic. One popular plastic frame material is polycarbonate. Frames made from this type of plastic are primarily associated with sport or safety glasses, as they offer the optimum balance of light weight, impact resistance and eye protection. In times past the frames were sometimes made from leather or bone.

The Bridge

The Bridge or Saddle Bridge links the rims of the two lenses and does what its name suggests, bridging the gap in between. The two teardrop shaped parts that hang down and grip your nose are known as the pads. The rims would just sort of slump onto your nose if it wasn’t for the pads, so a small round of applause for pads, please. (At least, for the times when they’re used. Glasses being as diverse as they are, not all types have them.)

The Temples

The arms that link the rims to your ears are known as the temples, because they pass over your temples. They keep your glasses in place when you turn your head or bend over. But they weren’t always there—although eyeglasses were first invented around the 13th Century, it wasn’t until British optician Edward Scarlett had the bright idea of inventing temples that passed over the ears in 1727 that people could be sure the things would actually stay on properly!

The Spring Hinge

The temples are joined to the rims by the spring hinge, which allows you to fold up your glasses and keep them shut. They also make the temples hug the head better and make for a closer fit. Hinge types vary in the amount of tension that they place on your temples, and some types can be adjusted. Hinges are most often made of either stainless steel or plastic. Stainless steel hinges tend to last longer but they often lack flexibility.

The hinge is joined onto the lug, or barrel which is attached to the lens rims. The most common type of hinge is the barrel hinge. A rim screw passes through the barrel and holds the rims tightly together, gripping the lenses and ensuring they stay where they should. Joined to the temples at the other end and slipping over the ears are a part called the Temple Tips. Maybe they should be called "Scarletts" in their creator’s honor?