Background: Jewish law requires a concrete act to put an agreement (contract, etc.) into effect - this act is called a kinyan (literally, acquisition), and is often carried out by handing over a garment or object, symbolic of a property transfer, and indicative of effectively making an undertaking. Such an act is binding on the parties.
In this case, it appears that the parties, to give binding effect to their undertakings in the document, have made a formal act of kinyan, in a manner that is effective in Jewish law.