English law. Those persons to whom a man, is delivered out of custody or prison, on their becoming bound for his appearance. 2. Mainpernors differ from bail: a man’s bail may imprison or surrender him up before the stipulated day of appearance; mainpernors can do neither, but are merely sureties for his appearance at the day; bail are only sureties that the party be answerable for all the special matter for which they stipulate; mainpernors are bound to produce him to answer all charges whatsoever.