The covenant by the grantor to make such other assurances as may be necessary to perfect the title is less extensively used in the United States than any of the other covenants for title, though its importance to the purchaser, it has been said, "can hardly be overrated."6 Under this covenant, the convenantor may be required to do such further acts as may be necessary on his part to perfect the title which the conveyance purports to pass, but the covenantee cannot demand that he do acts which are unnecessary, or which it is impossible for him to do. The remedy under this covenant is more often by a suit for specific performance than by an action of damages, as in the case of the other covenants.7