Re reading my post: I think I stated it poorly. It's not so much that a rod is for the left or right side, but they have an offset which must be positioned relative to the rod next to it. Once assembled on the pistons, you then have a set of "lefties", and a set of "righties". Also, most pistons have an offset, usually with a dimple to indicate position relative to the front of the engine.

And there have been some engines designed with perfectly symmetrical rods and pistons.