the way to tell is to lay one(or both) of the wings down flat. turn them so that the bumpier sides are facing up(the bumps are from the feathers being pulled from the follicles) If it is a full wing(drumstick and wingette,) there should be a pointed end. if you face the drumstick nub(handle, bone, whatever you call it,) inward, you can tell... it will be pretty obvious. if the nub is facing the left, it is the right wing and vice versa
