Md. Code, Commercial Law § 22–301

Terms with respect to which confirmatory records of the parties agree or which are otherwise set forth in a record intended by the parties as a final expression of their agreement with respect to terms included therein may not be contradicted by evidence of any previous agreement or of a contemporaneous oral agreement but may be explained or supplemented by:

(1) Course of performance, course of dealing, or usage of trade; and

(2) Evidence of consistent additional terms, unless the court finds the record to have been intended as a complete and exclusive statement of the terms of the agreement.