Can a Person Use an “X” as the Signature on Legal Documents?

Sometimes persons become physically disabled to the point that they can no longer write their name as they once did. Can a person in such a condition still create valid legal documents?

As long as a person places his or her “mark” on the document indicating that he or she has READ and UNDERSTANDS FULLY what the document is providing, and as long as there are witnesses to the fact that the person has agreed to the terms of the document and has made his or her mark indicating as much, the document should be valid and binding regardless of how the signature looks.