Glasses can be used to start a fire by concentrating the sun's rays and sparking tinder.

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If you've been called "four eyes" in the past, consider yourself lucky. In a survival situation, glasses can help you accomplish two very important things: getting rescued and building a fire.

Use your glasses to reflect the sun's rays to create a distress signal. Rescue personnel or a passerby will see the flashing, allowing them to locate you more easily. You can also dismantle your glasses if necessary and bend the wire frames to make hooks or small tools.

Starting a fire with glasses is much like starting a fire with a mirror (or a polished soda can). You must have a convex lens, usually found in prescriptions for farsighted­ness. Also, the lens should be made of glass (some lenses today are made of plastic).

To start a fire with a lens, first collect some tinder -- lint from your socks, Spanish moss or anything that's lightweight and will ignite quickly. Hold your lens about 1 foot (30 centimeters) from the tinder, angle it until the sun begins concentrating on a small spot and wait for the tinder to start smoldering. Then, gently blow on the tinder to ignite it completely and start adding kindling until the fire is stable.

To find out more about which items in your pocket or purse could help you in a survival situation, follow the links on the next page.