The most common document used in estate planning is a will. A will is a legal declaration (usually written) that makes disposition of your property upon your death. If you die intestate (without a will) state statutes control distribution of your property. Every person over the age of eighteen years and of sound mind may dispose of his/her estate by will. A will may be entirely written in the hand of the testator. This is called a holographic will. This type of will does not have to be witnessed. However, just as you would not attempt surgery on yourself, it is normally not advisable to attempt to write your own will. A will prepared by an attorney who practices in estate planning should ensure that it is properly worded, and just as important, properly executed. There are specific requirements that must be met with respect to the execution (signing) of a will. Oklahoma statutes and case law concerning the execution, interpretation and construction of wills have developed over many years. Therefore, using a will as part of your estate plan provides you with the security of proven law. Your will can be revoked or modified at any time as long as you are of sound mind. The document normally used to modify or change a will is called a codicil.