I keep forgetting to mention the new (well, newish) look of the Toronto Police Pipe Band website, which is much more multimedia friendly, more informative and a little more fun. Check it out.
WRIT OF MAINPRIZE, English law. A writ directed to the sheriff (either generally, when any man is imprisoned for a bailable offence, and bail has been refused; or specially, when the offence or cause of commitment is not properly bailable below) commanding him to take sureties for the prisoner's appearance, commonly called mainpernors, and to set him at large. 3 B]. Com. 128. Vide Mainprize.
A Law Dictionary, Adapted to the Constitution and Laws of the United States. By John Bouvier. Published 1856.