An undertaking, in the form of a covenant, on the part of the vendor of real estate to do such further acts for the purpose of perfecting the purchaser’s title as the latter may reasonably require. This covenant is deemed of great importance, since it relates both to the title of the vendor and to the instrument of conveyance to the vendee, and operates as well to secure the performance of all acts necessary for supplying any defect in the former as to remove all objections to the sufficiency and security of the latter. Piatt, Cov. : Rawle, Cov. 98, 99. See Sugd. Vend. 500; Armstrong v. Darby. 26 Mo. 520.