from The Century Dictionary and Cyclopedia
- Made in pairs one member of which is adapted to the right and the other to the left side, as boots, shoes, gloves, etc.
- Symmetrical with regard to a central plane: as, right-and-left engines.
- Having both a right-hand and a left-hand thread: said of screws. Bolts and screws for certain purposes are sometimes made with both threads cut on one piece.
Sorry, no etymologies found.