Wiktionary
working part
n. (context rope English) The section of rope between the working end and a knot being made.
Usage examples of "working part".
She had no doubt this was just another scenario created for themthe system appeared far too primitive to be an actual working part of the shipbut, because of its availability, hydrogen was the default fuel and should anything happen, should the bugs reappear, the last thing she wanted was a stray shot damaging one of those tanks.
A solution that might result from this process would be for the druggist to give the patient the drug, and the couple, in turn, would agree to pay for it by working part-time for the druggist after the patient gets well.
My kids are all in school now, so I thought I'd try working part-time.