How to position the player for climbing down a ladder?

Hello
I have a vertical ladder.
When the player is at the lower floor, he can easily start climbing up.
While the player is on the ladder, he can normally climb up and down.
However, when the player is at the upper floor, I have no idea how the player is supposed to start climbing down. He always falls…
Is there a way to position the player automatically on the ladder in climbing position when he walks over the top part of the ladder?

Thanks in advance