A step ladder can be anything from a couple of treads to help you reach high shelves to a multifunctional model with numerous adaptations. However, despite the huge variety available, there are a few key features common to all quality step ladders, which we explore below.

• Stability: Look for good width between the legs so the ladder doesn't rock sideways. Some actually angle outward to enhance this. We like step ladders with flat, solid treads that are comfortable and supportive. Ladders with rubber or plastic feet are also desirable because they won't slide on smooth flooring.

• Durability: Before you buy, check rail thickness, which is a good indicator of structural strength. Also check hinges and joints; they should be made of materials that resist corrosion.

• Mobility: Step ladders get moved around a lot. A lightweight step ladder can be beneficial for this reason.

Most step ladders are a straightforward construction of two or more steps. They fold flat for easy storage. Popular variations may include a platform at the top, an upper hand hold/safety rail, or a tool/utility tray.

Some step ladders have legs that are offset at different heights. These are designed for stair work. Additional angle settings may also be possible, and the item may open flat to create a taller standard ladder.

The most common size for home use is the six-foot step ladder. These are used for a multitude of indoor jobs and are tall enough to reach many outdoor rooflines – handy if you need to clear or repair your gutters.

Of course, there are step ladders of many different heights to choose from. Two- and three-tread models make it simple to access high storage spaces and are compact enough to store almost anywhere. At the other end of the scale are very tall step ladders; the tallest model we looked at reaches to 21 feet. Tall step ladders are ideal for tradespeople who work on commercial buildings; they provide a convenient platform for tasks like suspended ceiling installation.

When choosing your step ladder, you may have a specific task in mind, but it's worth thinking about other times when your purchase will come in handy. For example, if you occasionally need to decorate your house or reach objects high off the ground, a multifunctional step ladder offers a convenient alternative to the traditional step ladder.

There are four materials generally used in the construction of step ladders: wood, steel, aluminum, and fiberglass.

Wooden step ladders are less common than they once were. Other materials simply offer greater strength and durability for the same cost. However, "ladder stools" and "library chairs" have great decorative appeal and can last a lifetime if looked after properly.

Steel step ladders are strong and relatively inexpensive. Smaller step ladders with tubular construction are light, but larger steel step ladders can be heavy. A step ladder with a finish coating may resist corrosion, but it can be prone to chips and scratches which then lead to rust.

Aluminum step ladders are popular because they offer good strength and a light weight. Aluminum is technically not as strong as steel, but a good aluminum step ladder may use larger sections and/or extra bracing to compensate while still retaining considerable weight savings. Additionally, aluminum does not rust. Even if your step ladder is aluminum, however, the hinges, joints, and tread fixings will likely be made of steel. As such, a protective coating may be needed to enhance longevity.

Fiberglass step ladders offer tremendous solidity, and though not perhaps as light as aluminum, they weigh far less than steel. Fiberglass is another material that doesn't corrode, but as with aluminum models, the steel fixings will need adequate protection. One major benefit of fiberglass is that it doesn't conduct electricity. Therefore, it is safe to use near cabling or power lines.

The duty rating is the maximum recommended weight a step ladder can hold. That's the total of the person plus any tools. A step ladder with a 250-pound duty rating is classified as "Heavy-Duty Industrial." A 300-pound model is "Extra Heavy-Duty Industrial."

Even small step ladders have a duty rating of 200 pounds and upward, so weight seldom a problem. However, you may need to consider load limits when it comes to industrial/trade applications.

How much should you expect to pay for a good step ladder? That's a difficult question because there are so many to choose from. Our recommendation is to choose based on the features you need rather than price. A good step ladder is a long-term investment. Buy high quality and you'll probably never need to replace it.

That said, you can find step ladders in the vicinity of $20 as well as $200; this applies to all construction materials. For example, an aluminum folding ladder with just two steps is likely to cost closer to $20, whereas an aircraft-grade aluminum step ladder with four or more steps is likely to cost closer to $200.

Q. I've heard that fiberglass step ladders can shatter. Is that true?
A. Though theoretically possible, it’s very unlikely unless the step ladder is subjected to severe impact. If the ladder were to be hit with a sledge hammer, for instance, it might shatter. But then, a steel or aluminum version probably wouldn't survive that kind of treatment, either!

Q. Do step ladders need any maintenance?
A. Mostly it's just a question of keeping them clean and dry. A little oil on the hinges periodically will keep them operating smoothly. Check that the ladder rungs and braces are secure before you use it, and never use a step ladder that is damaged in any way.