COMPLEMENTARY
The left hand washes the right one as the right one washes the left .
Complementing one another is basic to mutual, syncretic glory.
Old Motown comes to mind, as do any number of older complementary agglomerations.
Two left feet or two right feet are mutually ineffective, hazardous!
Complement someone or something when and where you can, as they or it will complement you, in turn. Every little bit helps.