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general::
Phrase(s): You scratch my back and I’ll scratch yours.
Fig. You do a favor for me and I’ll do a favor for you.; If you do something for me that I cannot do for myself, I will do something for you that you cannot do for yourself. • I’ll grab the box on the top shelf if you will creep under the table and pick up my pen. You scratch my back, and I’ll scratch yours.
McGrawhill's American Idioms And Phrasal Verbs