If you're like most kids, you've probably broken a bone. Or maybe you know someone else who has. That means you've seen a cast. Do you know how a cast works? What it's made of? Whether it's OK to draw on one? Keep typing to find out more.

Think of a cast as a big bandage that has two layers. Inside there is a soft cotton layer. It rests next to the skin. This makes the cast more comfortable. It also protects the skin. Outside there is a hard outer layer. This layer prevents the broken bone from moving. Sometimes you can choose how your cast looks. You can pick cool colors or patterns.

Casts come in two types. The first type is made of plaster of Paris. You may have used this material for arts and crafts. Plaster of Paris is a heavy white powder. When it's mixed with water, it forms a thick paste that gets hard fast.

The second type is made of fiberglass. This is a plastic material. It can be shaped. Fiberglass casts come in lots of colors. These casts are lighter and stronger than plaster casts. That makes them easier to wear. It also makes them last longer.

Your doctor will make sure that all the pieces of your broken bone are in their proper places. Then he'll put on the cast to prevent the pieces from moving while they heal. This way they'll grow back together into one bone. It also prevents injury to the area around the bone. Most kids with broken bones say it actually feels much better once the cast is on.

How long do you have to wear a cast? Sometimes it's only for a few weeks. Sometimes it's much longer. It depends on the type of injury you have. It also depends on how badly the bone was broken.

Your doctor may put on the cast himself. Usually, though, another person who is specially trained to put on casts does it. First, he will measure the exact amount of soft cotton you'll need. Second, he will wrap several layers around the broken area. Third, he will dip the plaster or fiberglass layer in water. This softens it so he can shape it. Last, he'll wrap it snugly around the cotton. Before the outer layer dries, the cast may feel quite heavy. In a short time you'll get used to wearing it.

The cast may be on your arm. If so, you may be given a sling. A sling is a wide piece of cloth with straps. The straps go around your neck. They are attached to the cloth that goes around your arm. This will help you support and carry the cast.

The cast may be on your leg. If so, you might get crutches to help you walk. Crutches let you keep the weight off the injured leg. Too much weight can prevent the bone from healing properly. Sometimes you get a special shoe to wear over the cast. The shoe lets you walk without putting too much weight on the cast. It looks clunky, but it's better than being in pain!

So now that you have a cast, what do you do? Here are some tips. First, if you have a plaster cast, you don't want to get it wet. Water will make the cast loose or even come off. Then it will not be able to keep the bones from moving. Also, the cotton padding beneath is hard to dry. If it gets wet, your skin may develop a rash or infection. That means if you take a bath, you have to cover the cast with a plastic bag. You can also buy a waterproof sleeve. Depending on where your cast is, you may have to take a sponge bath. You use a wet sponge or cloth to clean the rest of your body. You can wash your hair in the sink or go to the beauty parlor. That way you don't risk getting the cast wet.

Luckily, some casts are also waterproof. This means you can get them wet without ruining the cast. Most of these are made of fiberglass. Also, the padding is not made of cotton. It is made of another waterproof material. With this type of cast you can take a shower or a bath without having to use a plastic bag or sleeve. You might even be able to swim! Be sure to check with your doctor first, though.

Second, never stick anything inside your cast. You could injure the cast or the skin underneath. But the skin under the cast often itches. What should you do? Here's a neat trick -- use a blow-dryer set on "cool." Blow air inside the cast. It really works, and it won't hurt.

Third, watch for cracks. Now, your cast may have cuts or cracks in it when it's put on. Doctors sometimes make tiny cuts in the side. This allows room for possible swelling. Many times your body will swell near the broken bone. This is the body's way of healing itself. The liquid under your skin protects the broken bone from further injury. But, your cast may also develop cracks on its own. This happens if it has been hit or crushed. Or it may have a weak spot. Your skin may swell underneath, too. If the doctor did not make a cut on the outside, the swelling may crack it. If you see a new crack, tell someone right away. You may have to see your doctor.

Fourth, watch your skin color around the cast. You may see your fingers or toes turning purple or blue. That means the cast is too tight. You aren't getting enough blood to those areas. Be sure to tell a parent right away. Your doctor will need to loosen the cast so you don't hurt the area more.

Last, it's perfectly okay for your friends and family to sign your cast. Permanent markers usually work best. Washable ones can smear. It's also fine to draw pictures on it. You can even decorate it with stickers. Be creative! This might make having a cast a little bit more fun.

Doctors use a special saw to remove a cast. It has a dull, round blade that vibrates up and down. The vibration is strong enough to break apart the fiberglass or plaster. It can't hurt your skin. The vibration may actually tickle you! But a word of warning. The saw can be very loud, almost like a vacuum cleaner. Just remember that it will sound much worse than it will feel.

You may want to keep your cast. Perhaps all your friends signed it. If so, just ask your doctor. Many doctors are happy to let people keep their casts.