This is the 15727th most frequent Russian word.
приточному
"Приточному" refers to something related to "supply" or "inflow," often used in contexts like ventilation systems (air supply).
Here, "приточному" refers to the house being adjacent or associated, indicating possession or proximity.
Ключ принадлежал приточному дому.
The key belonged to the adjoining house.
The word "приточному" here describes the entrance as being adjacent or part of a building, which is a contextual or locative usage.
Он подошёл к приточному подъезду.
He approached the adjoining entrance.
In this sentence, "приточному" is used to connect the story with the occasion, thus giving it a relational function.