A more thorough explanation:

The Bill of Middlesex is a legal process used by the Court of the King's Bench in Middlesex to gain jurisdiction over a defendant who lives in a county outside of the court's jurisdiction. This is done by alleging a fictitious trespass in a county where the court has jurisdiction.

For example, if a defendant lives in Essex but the plaintiff wants to sue them in Middlesex, the plaintiff can file a Bill of Middlesex alleging that the defendant committed a trespass in Middlesex. This gives the court jurisdiction over the defendant, even though they live in a different county.

Once the sheriff receives the Bill of Middlesex and confirms that the defendant is not in the county where the alleged trespass occurred, a latitat is issued to the sheriff of the defendant's actual residence. This is a writ that commands the sheriff to take the defendant into custody and bring them before the court to answer to the plaintiff's claim.

The Bill of Middlesex was used in England in the 18th century and was a controversial practice because it allowed the court to gain jurisdiction over defendants who lived far away and may not have committed any actual trespass in Middlesex.