Because of their relative proximity, the three airspace cylinders affect one another significantly, which creates congestion not just because of volume but because pilots have to thread the needle and fly needlessly intricate approach routes in order to comply.

ECONOMIST: Business travel

Acus has several meanings including a "single-prong hairpin" or "needle and thread, " she says.

WSJ: On Pins and Needles: Stylist Turns Ancient Hairdo Debate on Its Head

But a needle and thread could.

WSJ: On Pins and Needles: Stylist Turns Ancient Hairdo Debate on Its Head

He showed it to an expert, who found the needle-and-thread theory "entirely original, " says Mr. Humphrey, whose own scholarly work has examined arenas for Roman chariot racing.

WSJ: On Pins and Needles: Stylist Turns Ancient Hairdo Debate on Its Head

The last scrutineer pierces each ballot with a threaded needle through the word "Eligo (elect)" and places it on the thread.

NPR: The Papal Transition: An Overview