The invention of ladders has been traced back at least 10,000 years, to a primitive cave painting in Spain. The ladder is a tool of man so basic in nature that it most likely took shape along with the discovery of fire, hammers, knives and the wheel.

The purpose of a ladder is very straightforward: to extend one’s reach. Using one is quite simple, too. However, as prehistoric man soon discovered, this wonderful invention could also slide, slip, tip or break, and, for the past 100 centuries or so, man has endured needless injuries through the chronic misuse and misunderstanding of ladders.

First, if you’ve got an old wooden ladder that’s rickety or broken, here’s what to do. Take your saw, cut it into pieces and use it for firewood. There is no excuse for using an unsafe ladder. It truly is “an accident looking for a place to happen.”

Choosing the right ladder starts with two decisions: type and size. There are two basic styles of common ladders: folding stepladders that open into a self-supporting triangle shape, and straight extension ladders that slide one upon the other and must lean on something for support.

Both can be used indoors or outside and their main consideration is height or maximum “reach.” For stepladders, add the ladder’s height plus four feet (for you) to determine total reach. Thus, to reach an eight-foot ceiling, you need at least a four-foot stepladder. A six-foot ladder is even better and it will also allow you to reach a 10-foot ceiling, and so on.

With extension ladders, the base and upper sections must maintain some overlap for support. The top rungs must extend at least two to three feet above the upper edge of a roof or elevated destination for safe access and hand-held support, which makes a 20-foot extension ladder only good for a 14- or 15-foot climb.

Other key considerations are the “duty rating,” which indicates how much weight a ladder will safely support and the type of material from which a ladder is made. There are five different official ratings for ladders, set by the American National Safety Institute, and it includes your weight plus what you carry:

Type 3 (Light Duty): up to 200 pounds

Type 2 (Medium Duty): 225 pounds

Type 1 (Heavy Duty): 250 pounds

Type 1A (Extra Heavy Duty): 300 pounds.

Type 1AA (Extra Heavy Duty Industrial): 375 pounds

These ratings are found on labels placed on the side rails.

Today’s ladders are constructed of: wood (which can be a bit heavy), aluminum (which is lighter), and fiberglass (which is both light and does not conduct electricity). Fiberglass also comes in colors that often designate duty rating.

Remember that even a perfectly good and correctly chosen ladder can still be extremely unsafe if not used properly. Be sure that stepladder legs are fully extended, that hinges are locked into place and that the feet are level and firmly planted.

With extension ladders, always place the bottom feet one-fourth the height of the ladder away from the wall. Thus, the bottom of a 20-foot extension ladder needs to be five feet out at the base to keep from tipping backward when your weight is added.

With stepladders, never stand on the very top cap, which usually reads: “This is not a step” (for good reason) or on the first step below the top cap.

With extension ladders, never stand on or above the third rung from the top. In either case, if you must do so to reach your goal, the ladder is too short — and so may be your days of health and welfare.

Good tips also include maintaining proper balance by keeping your hips between the side rails. Leaning too far out in either direction may suddenly and seriously bring sideways motion and gravity into play.

For tips from James and Morris Carey, go to www.onthehouse.com or call the 24/7 listener hot line, 800-737-2474. The Careys are also on KRKO (1380-AM) from 6 to 10 a.m. every Saturday.