A Notnagel (lit. "emergency nail" or "nail in need") is an iron nail carried by firefighters of oldto be used when an escape from an upper floor through the interior was blocked: It could be hammered into an outside window or door frame so that a rope could be put through the hole, allowing the endangered firefighter to rappel down to safety. Now used to indicate a last-minute substitute or remedy, a stopgap solution. I like this modern, figurative use of the term because of its association with a real and remarkable object (Source)
Note on pronunciation: Both the "o" and "a" are long and no diphthongs. Especially the "a" is pronounced like the "a" in "father", not like the "a" in "bagel". But the "g" is voiced as in "bagel".