Green’s Dictionary of Slang

1. (US, also rubberglue, soft heel) a private detective; a store detective; a railway detective.

[1913		Van Loan ‘For Revenue Only’ in Lucky Seventh (2004) 216: A large, calm, horse-faced man in a gray uniform came in on rubber heels.].
1927		‘Jargon of the Und.’ in DN V 463: soft heel, A railway detective.
[1928		Leamington Spa Courier 19 Oct. 10/6: Edward Wynn is a rubber-heeled detective].
1930		G. Milburn ‘Me and My Bindle’ in Hobo’s Hornbook 262: When standing there before me was the Podunk rubberglue.
1931		Irwin Amer. Tramp and Und. Sl. 176: Soft Heel. – A detective; one who wears rubber or ‘soft’ heels.
1949		Monteleone Criminal Sl. (rev. edn).
1950		Goldin et al. DAUL 201/2: Soft-heel. (Hobo) A railroad detective.
1989		J. Morton Lowspeak.

2. (also rubber-heeler) someone who spies on their fellow employees; thus rubber heel boy, rubber heel inquiry, rubber-heel mob.

1942		Berrey & Van den Bark Amer. Thes. Sl.
1959		M. Pugh Chancer 91: You fancy yourself as a ‘rubber-heeler?’ The phrase usually applied to policemen, sent to check on another policeman.
1970		‘Metropolitan Police Sl.’ in P. Laurie Scotland Yard (1972) 327: rubber heel: internal police investigation (in contrast to the noisy steel-tipped heel of the traditional police boot).
1989		J. Morton Lowspeak.

3. (US black) as ext. of sense 2, a plagiarist.

1941

‘Digg Mee’ ‘Observation Post’ in N.Y. Age 13 Sept. 9/7: If you’ll promise to stay on keel, if you’ll stop being a ‘rubber’ heel, I’ll personally teach you how to spiel.

4. (US prison) in pl., meatloaf [negative comment on the dish’s consistency/flavour].

1949

N. Algren Man with the Golden Arm 208: ‘Rubber heels and fisheyes again’ was the word on the meatloaf and tapioca.