I think you may be referring to a marriage bond, also known as a marriage allegation, which was required to support the issuing of a licence to marry, for instance where a person under the age of twenty one wanted to marry.
These bonds were contracts in which the applicant (usually the groom) pledged that there was no impediment to the proposed marriage. Usually some evidence that the father of the underage person did not oppose the marriage would be required. I have seen bonds where the second bondsman swears that he has been told by the father that there is no objection, and if he (the second bondman) is later found to have lied, he would have to pay a bond amounting to several hundred pounds. Marriage licences and the process of the bonds was normally handled by the Anglican Bishop in whose diocese the marriage was to take place, so that the first place to look. There were some special rules about who could issue a licence where the bride and groom lived in different dioceses. Ancestry and FindMyPast have special collections of marriage bonds for various parts of the country. Incidentally the procedure was different in Scotland which is why some couples went to marry at Gretna Green.
