What's the largest -- and possibly the most dangerous -- tool in your house? A table saw perhaps? Or a sledge hammer? Think again. How about your ladder?

Not many of us consider ladders as tools, but that's exactly what they are. Ladders allow us access to burned-out light bulbs, gunk-filled gutters and overhanging branches. They can be used -- and misused -- in a seemingly countless number of ways.

According to the American Ladder Institute, "ladder misuse" accounts for almost 500,000 falls each year and about 165,000 visits to emergency rooms. About 300 deaths a year can be traced to accidents involving ladders.

So before tackling fall chores such as cleaning the gutters, brush up on a little ladder safety, because many of those half a million falls can be traced to common mistakes.

The most obvious, said Ron Pietrzak, executive director of the Chicago-based American Ladder Institute, is overreaching -- by leaning too far to the side or by climbing too high. Another common mistake, Pietrzak said, is known as "walking the ladder." You position the ladder in one spot, then decide it's not in the right place. Instead of climbing down and repositioning the ladder, you stay put and attempt to wobble the legs and "walk" the ladder to the desired position.

Pietrzak figures if more people showed common sense, like placing legs on steady ground, and were aware of a ladder's duty rating, or the weight it can bear, injuries would be reduced significantly. Unfortunately, too many people choose shortcuts over safety. "I could tell you some horror stories, some crazy, stupid incidents that get people killed," he said.

Take, for example, the sailboat owner who was working on his vessel, which was stored in the driveway. According to Pietrzak, the owner made a rudimentary ladder from old lumber so he could complete work on the mast. He used it several times without incident. When an exterminator came to work on the house, the owner let him use the homemade ladder. Twice.

The second time, the exterminator fell and was paralyzed. A lawsuit is likely.

"Everybody is pointing fingers," Pietrzak said, "asking why the homeowner didn't just purchase an extension ladder."

The right extension ladder, with the proper duty rating, might have made the difference. Duty rating defines the load-bearing weight of ladders, which are designed to support one person plus materials and tools. The American National Standards Institute determines duty rating and prints the information on a color-coded label, required by the Consumer Product Safety Commission, on the leg of every ladder.

Duty ratings run from Type III, with a capacity of 200 pounds, to Type 1AA, which can hold 375 pounds. Type 1A and 1AA ladders, built for commercial and industrial use, are more expensive than "household" or Type II and III ladders but can be purchased by homeowners.

Another important label is located a couple of steps below the top step; it warns users of the danger of falling if they climb above a designated point.

The label also will tell users if the ladder is the right tool for the job, Pietrzak said. There is a rule of thumb to determine the proper height, or length, of the ladder needed for a particular task: Identify the height of the job, then subtract the user's height. This number is the highest standing level of the ladder to be used.

For example, if the job height is 13 feet, and the height of the user is 6 feet, a ladder that allows a standing level of 7 to 8 feet is needed.

Pietrzak advises using the ladder as it was intended. "Don't lean a stepladder against a wall and try to use it as an extension ladder," he said.

Finally, aluminum ladders should not be used when working with electricity or near electrical lines. Use nonconductive wood or fiberglass ladders instead.