Green’s Dictionary of Slang

blow job n.2

(US und.) safebreaking using explosives.

J. Webb Badge (2006) 302: BLOW JOB Where explosive is used on a safe.
[US]L. Shecter On the Pad 179: There’s also the old-fashioned blow job, which nobody uses anymore. You blow the whole goddamn safe. It makes a helluva bang.