itself. Erwin v. City of Palmyra, 119 S.W.3d 582, 584 (Mo.App. E.D.2003). Only when the language of the deed is “unclear and ambiguous” do we resort to the rules of construction and consider extrinsic evidence. Id. at 584. A contract is not ambiguous simply because parties disagree about its meaning. Id. Rather, “an ambiguity arises ‘when the terms are susceptible of more than one meaning so that reasonable persons may fairly and honestly differ in their construction of the terms.’ ” Id., quoting Chehval v. St. John’s Mercy Medical Center, 958 S.W.2d 36, 38 (Mo.App. E.D.1997). Extrinsic evidence cannot be used to create an ambiguity, it must appear from the four corners of the contract itself. Id.; see also White v. Meadow Park Land Co., 240 Mo. App. 683, 213 S.W.2d 123, 126 (1948) (<HOLDING>). We find nothing unclear or ambiguous in the
holding that if the language of the statute is clear and unambiguous a court must derive legislative intent from the words used without involving rules of construction or speculating as to what the legislature intended holding evidence that would contradict add to or subtract from or affect the construction of a valid complete and unambiguous written instrument is inadmissible under the parol evidence rule holding if the language of a deed or other written instrument is clear and unambiguous the intention of the parties is gathered from the instrument it is what the grant or said and not what he intended to say recognizing that the primary source for determining whether a contract is clear is the text of the document itself when an instrument is unambiguous it construction and legal effect will be based upon what is found within its four corners holding that for purposes of the aggravated assault statute if the instrument used is a firearm as defined by section 7900016 then that instrument is a deadly weapon as a matter of law  regardless of whether it is loaded or capable of being fired and holding that for purposes of the aggravated assault statute if the instrument is not a firearm then courts are to apply an objective test and look to the nature and actual use of the instrument and not to the subjective fear of the victim or intent of the perpetrator in determining whether the instrument is a deadly weapon