Green’s Dictionary of Slang

(US campus) a home-made tool, which approximates a car’s starting-handle.

1967

D. Simmons ‘Terms Used in a Men’s Dormitory’ in AS XLII:4 229: rat-fucker, n. A tool, usually made from a straight piece of metal coat hanger, [...] in such a manner that it ultimately has the shape of an old car crank handle.