On Mon, 24 Jun 2013 10:56:44 -0400, Don Wiss wrote:

The back yard neighbor has put up a fence that is 1 1/2" on my property.

I went through this a few years ago.

In California, the law, as I remember it, is weird about the subtleties
surrounding these two types of property disputes:
a. prescriptive easement
b. adverse possession

In the first case, your implied consent allowing the fence to overshadow
your property line can be used in the future to allow a judge to prescribe
an easement (usually for the *subsequent* property owner).

In the second case, the neighbor is knowingly overshadowing your property
line, against your will, and you allow it for a long enough period that
the neighbor actually can lay claim to the land.

In both cases, if you merely write a lease (e.g., for $1 a year), that
allows the overshadowing, you maintain clear rights to the overshadowed
land.