My old bike* is permanently out of commission, and I'm temporarily on a borrowed bike. It's fine, but it felt not quite right. I swapped over my old saddle (Brooks¸c20yrs old) and, with the help of a tape-measure, adjusted the positioning to be as close as possible to my old bike: now it feels perfect (and has better brakes!).
*Very old bike, bottom bracket worn and impossible to remove from the frame