Green’s Dictionary of Slang

(drugs) to cut up lines of a narcotic, usu. cocaine.

1997		N. Barlay Curvy Lovebox 59: Kingsley starts rackin’ up lines on his mirror.
2007		L. Redhead Cherry Pie [ebook] ‘Rack me up another line’ [...] They both had another snort.
2009		R. Milward Ten Storey Love Song 93: [S]he listens to the boys cram in the bog, and they [...] rack up a couple of white worms.
2011		J.J. Connolly Viva La Madness 299: Chip calmly gets a knotted plastic bag out of his jacket — a couple of ounces [...] ‘Rack ’em up, Chip,’ says one of the younger brothers.