I know about this legal concept because I was a party to this when I bought my house. It came with a sheaf of paperwork, including a signed and dated receipt for the construction of the fence across the back of the property. The receipt indicated the fence had been built about 20 years prior; the only problem was that it extended about 5-10 feet onto the neighbor's property. You could see it from their driveway and the main road, too. Apparently the neighbor never bothered with it, and when the current owner bought that property, the surveyor informed him of the discrepancy. The new neighbor approached me and admitted I could try for adverse possession, but we worked it out amicably.