the metal door *off* the loading platform

[suprunp]

The rolling metal door off the loading platform was closed, but she walked up to it anyway, aware of the scent of rotting produce on the cold, greasy concrete where the snow had melted.
(The Memory Keeper's Daughter, Kim Edwards)

What does 'off' indicate here?
Does it mean that the rolling metal door was next/near to the loading platform?

Thanks.

[5jj]

The rolling metal door leading from the loading platform was closed...,