A friend sent me this unattributed scan, the first drawing I can recall seeing about one of the small secrets of Savile Row. And that is the Savile Row fold for trousers which, until the felted hanger bar, was probably the best way to keep one's trousers from falling off the hanger.
The fold was important as suit hangers with locking trouser bars never worked worth a fig for me. I would get to my hotel and find my trousers inevitably puddled in the bottom of their suit bag. Even a little movement in the closet was sometimes enough to send them to the floor, and if the trousers did stay in place it was because the locking bar was putting a crease in them.
The best solution of course are wooden suit hangers with felted trouser bars. Everything remains in place, without the need for a Savile Row fold. But the fold is the next best thing.