Role of voidance and necessity of mortgage contract in mortgage of Commercial documents

Merchants put the commercial documents to security in commercial relationship with each other and banks. That is called "mortgage of commercial documents" and this action is computed by endorsement method for security. Commercial law of Iran hasnt foreseen such a institution to mortgage for commercial documents. So court judges and lawyers analyze the case of mortgage of commercial documents by civil law and mortgage contract; but they face with some problems to do such action. One of these problems is voidance of mortgage contract from mortgagee. This essay attempts to present a solution to this problem. in the name of god.