Green’s Dictionary of Slang

nigger rig v.

[nigger n.1 (1) + SE rig]

[1950s+] (US) to perform second-rate, sloppy work; thus as n., a bodged job, a piece of do-it-yourself assembly.

In derivatives

nigger-rigged (adj.)

[1950s+] (US) characterized by bad workmanship.