Green’s Dictionary of Slang

knap v.

[var. on nap v.1 ]

1. [late 17C–early 18C] (UK gambling) to use sleight-of-hand to cheat in dice-play.

2. [mid-18C] (UK Und.) to swear, to take an oath.

3. [mid-18C] to arrest.

4. [late 18C–19C] (UK Und.) to steal, to take, to receive; thus knapper n., a thief; knap a clout, to steal a handkerchief; knap seven penn’orth, to receive a 7-year sentence; knap/nap the glim, glue, to catch venereal disease; knap the swag, to grab the plunder.

In phrases

knap a jacob from a danna-drag (v.) [jacob n.1 (2) + danna n. + drag n.1 (2b)]

[early 19C] (UK Und.) to steal the ladder from a nightsoil cart in order to use it for burglaries.

knap the ding (v.) [ding n.1 ]

[early–mid-19C] (UK Und.) to take or steal what has already been stolen.

knap the rust (v.) [SE rusty, of horses, refractory]

[19C] to lose one’s temper.

knap the stoop (v.) (also nab the stoop, nap...) [SE stoop, the position into which the prisoner is forced]

[late 18C–mid-19C] to be placed in the pillory.