Green’s Dictionary of Slang

sap n.3

[SE sapling, from which the weapons were orig. made]

1. (US tramp) an act of clubbing.

[US]J. Flynt Tramping with Tramps 389: A hobo has recently written me that this word is gradually giving way to ‘saps,’ because the sticks and clubs used in the fracas come from saplings cut down for the purpose.
[US]G. Milburn ‘Hellelujah, Bum Again’ in Hobo’s Hornbook 99: I stayed there and drank till a fly-mug came in, / And he put me to sleep with a sap on the chin.

2. (US, also sapstick) a small club, orig. of wood, latterly a small leather ‘bag’ filled with sand, lead shot or similar material.

[US]D. Runyon ‘The Informal Execution of Soupbone Pew’ in From First to Last (1954) 69: He was there forty ways with a sap and gat, and he’d shoot as quick as he’d slug.
[US]Morn. Tulsa Dly World (OK) 13 June 19/3: Sap or sapstick — A crutch, cane or club .
[US] ‘Gila Monster Route’ in N. Anderson Hobo 195: He shook them out of their boozy nap, / With a husky voice and a loaded sap.
[US]‘Goat’ Laven Rough Stuff 14: The boys here [...] carry a gaspipe, or a sap (blackjack, which you might describe as a pocket club) wrapped in newspaper.
[US]R. Chandler Farewell, My Lovely (1949) 151: While he was still groaning I knocked him cold with the sap.
[US]‘William Lee’ Junkie (1966) 47: The Independent has special cops [...] but they don’t carry guns. Only saps.
[US]C. Himes Run Man Run (1969) 57: I sapped him with my sap.
[US]J. Wambaugh Choirboys (1976) 97: The gun, the badge. Not to mention the oversized sap hanging from the sap pocket.
[US]R. Price Clockers 9: Two-hundred-pound white bums with lead saps and Glock Nineteens.
[US](con. 1964–8) J. Ellroy Cold Six Thousand 24: Sap shots. Hard steel meets plywood and glue.
[US](con. 1960s) J. Ellroy Blood’s a Rover 25: He carried [...] a beaver-tail sap on a thong.
[US]R. Hobbs ‘Brass’ in ThugLit Feb. [ebook] ‘A sap or stun gun knocks a guy out’.
[UK]‘Aidan Truhen’ Price You Pay 31: They get me coming out of the elevator. Heavy hands and a billy club or a real old-fashioned sap.
[US](con. 1962) J. Ellroy Enchanters 86: The sap stitches severed an earlobe and cut through his lips.

In compounds

sap glove (n.)

(US und.) a glove with lead or similar inserts that intensifies a beating.

[US](con. 1962) J. Ellroy Enchanters 8: Harry and Eddie whomped him with sap gloves.
sap man (n.)

(US) a beggar on crutches.

[US]N.-Y. Trib. 10 May B1: First of all, there are the cripple[s], the men on crutches, who are known as ‘sap’ men [...] Go down to ‘Dan’ O’Rourke’s saloon on Park Row, the time honored hangout of the cripple beggars, the ‘crutch’ or ‘sap’ men, and half a dozen sad faced mendicants are all that survive of the score or more who worked the city.