What is a one-sentence summary of the following article?
There are a few basic parts of the extension ladder that you should be familiar with before you attempt to use it. Here are the most important:  The safety shoe or foot of the ladder consists of the pads that are designed to be in contact with the ground when the ladder is in use. These typically will swivel or rotate slightly in order to be make better contact with the surface the ladder is on. The fly section is the portion of the extension ladder that will be extended upward. This is the portion that you will climb as you get closer to the top. Additionally, it should be noted that some extension ladders have a two-part fly (and three primary ladder components in total). The base section is the portion of the extension ladder that will remain in place. When you begin to climb the ladder, you will start out on the rungs of this section. The rung lock is attached to the fly and is used to keep the fly in place by fitting over the top of a rung of the base or fly section underneath. It will essentially act as a bracket, and the fly will not be able to slide down after weight if put on it. The rope and pulley are used to extend the largest of extension ladders. Smaller ladders do not have this component, but larger ones are essentially unusable if this is broken. Serious injuries resulting from the use (or misuse) of extension ladders are so common that they have developed a bit of a reputation. Knowing how they earned that reputation--and how those accidents could have been prevented-- can help you stay safe.  Extension ladders typically only have two points of contact with the ground. Some varieties of smaller ladders fold out to create four separate points of contact with the ground. Extension ladders typically have nothing other than the "feet" or "shoes" on the two side rails. Consequently, they can be a bit unstable. Extension ladders are among the tallest available in retail sales outlets. It is not merely that their height makes for longer falls (though that is true as well). Instead, the height only accentuates the preexisting instability issues. Think of the ladder as a lever. When you climb the ladder, the weight is actually moved closer to the end of the lever. People commonly misuse extension ladders. Because of their instability issues, there are certain precautions that must be taken. First, two people must be involved in the use of the ladder. When one person climbs, another must be available to "foot" the ladder (hold it in place). Secondly, the ladder cannot be used a vertical or near-vertical angles. Instead, they must bed tilted or leaned on to another object for support as a person climbs to the top (more on this in a moment). This will minimize the "leverage" issue previously noted.

Summary:
Familiarize yourself with the parts of the extension ladder. Understand why extension ladders are considered dangerous.