В предыдущей фразе говорится, что настоящий договор является окончательным договором между сторонами и заменяет все предыдущие, etc.
Спасибо.

The parties further agree that this Agreement may not in any way be explained or supplemented by a prior or existing course of dealings between the parties, by any usage of trade or custom, or by any prior performance between the parties pursuant to this Agreement or otherwise, and that this Agreement may be modified or amended only in a writing signed by the parties.

a) A course of dealing is a sequence of previous conduct between the parties to a particular transaction which is fairly to be regarded as establishing a common basis of understanding for interpreting their expressions and other conduct.

(b) A usage of trade is a practice or method of dealing having such regularity of observance in a place, vocation, or trade as to justify an expectation that it will be observed with respect to the transaction in question. The existence and scope of the usage are to be proved as facts. If it is established that the usage is embodied in a written trade code or similar writing, the interpretation of the writing is for the court.

ИМХО что-то типа наших "обычаев делового оборота"