A prescriptive easement is a lot like taking over land from somebody else. At first glance, many people equate prescriptive easements to stealing, because they are acquired without paying money, by using the land without permission. A better understanding of what is required to establish a prescriptive easement, and why it is even allowed, usually calms that sentiment.
A prescriptive easement is defined as an easement created from an open, adverse, and continuous use, hostile to the true owner's title over a statutory period. You may be thinking, "Huh???" This definition may sound like "bla bla wa wa" to you, but it is a concise way to articulate why it is difficult to get a prescriptive easement over another person's property. If you want to establish a prescriptive easement over someone else's property, you have to be using the property in some normal kind of easement way, like a pathway, driveway extension, garden, etc. Therefore, you can put away the monster truck for now.
As an example, assume that you have a driveway on the edge of your property that runs alongside your neighbor's property. This driveway happens to have been put in place on what you thought was the border but turned out to be five feet on your neighbor's side. This use must be open and notorious. What this means is that you cannot conceal your claimed easement from everyone, especially the property owner. So, running across the back of your neighbor's yard at two in the morning, and only when you know for a fact that the neighbors are on vacation and could not possibly find out, would probably not count as an open and notorious use. The example of the driveway, however, is rather apparent to everyone.
The next important qualification to establish a prescriptive easement is that the use must be adverse. What this means is that the use must be done without permission from the owner. So, in our example of the driveway along the border of your and your neighbor's properties, your neighbor cannot tell you that she knows that part of the driveway is on her land, but that it is OK for you to keep the driveway there. If your neighbor does this, then she has given you permission, and your claim is no longer adverse to her interest. This does not mean, however, that your neighbor would have to know about your use, only that they cannot have given you permission.
Finally, the use has to be continuous for the statutory period. This varies depending on what state you are in. Continuous use does not necessarily mean that it has to occur every day or even every week. In other words, continuous is not the same as constant. When it comes down to it, a court will most likely have to decide whether or not a use occurs often enough to be considered continuous. In our example of a driveway along your property border with your neighbor, the use would most definitely be continuous, as the driveway is there every minute of every day, and you use it on a relatively regular basis. Thus, if you put in a driveway on what you thought was your land, but that later turned out to be your neighbor's land, and use the driveway for 15 or more years, odds are that you have gained a prescriptive easement in that portion of your neighbor's land that the driveway sits on.