Transferring an Object From One Domain to Another
Hotza'ah can occur at the threshold of a building. The distance may be short; the defining act is moving an object from one halachic domain to another.
Lifting, carrying, and placing
The complete melacha includes lifting an object from its resting place, moving it, and placing it in the second domain. In the language of halacha these stages are akirah, movement through the intervening space, and hanachah.
Passing an object to another person, resting it along the way, or using a threshold can change who performs each part of the act. It does not turn the transfer into an ordinary permitted act. Chazal prohibited arrangements that divide or approximate the melacha, and a small change in where the object rests can change the question.
A doorway and the street
A building interior, vestibule, front steps, fenced yard, sidewalk, and street may not all have the same status. A permitted key arrangement or storage plan therefore depends on the actual doorway and route.
The same issue arises when handing a bag through a doorway, taking a stroller down the steps, placing food outside for someone else, or retrieving an object left near the entrance. The distance can be only a few inches; crossing the boundary between domains is what matters.