Eleven at night is the kindest hour a hotel lobby offers. The check-in queue dissolved around eight. The restaurant is seating its last table and beginning, quietly, to want its evening back. Most people crossing the floor are guests coming home from dinner, and a few of them have someone with them or someone expected upstairs.
A visit to a guest's room at that hour is an ordinary thing for a hotel, and nothing clever has to be arranged around it. What makes the arrival easy is a little preparation on both sides of the door.
What she knows before she sets out
She has looked at the building before leaving: which side the lifts are on, whether the lobby is one room or a sequence of rooms, whether the bar sits between the entrance and the lift bank. She has the room number, or knows it will come in the thread once she is on her way. If the guest mentioned a house rule, that visitors after ten are collected from the lobby, that a name is given at reception, that the lifts need a card, she knows that as well, because it was in the booking message.
Crossing the lobby
She comes in as any visitor would, dressed for the weather and the building, with one small bag on her shoulder. Where reception asks visitors to announce themselves, she gives the room number and waits for the call upstairs like anybody else calling on a guest. Where the hotel prefers visitors to be collected, the guest comes down and the two of them go up together. Where nothing is asked, she goes to the lift.
A night porter at eleven is running a building: late check-ins, a key card that has stopped working on the sixth floor, a taxi for an early flight. Asking a visitor which guest she has come to see is part of that job, and the question gets a plain answer.
Then the lift, and the floor
With the room number in hand, the corridor stage lasts as long as it takes to walk a corridor. The knock is soft enough to reach one door rather than three, and it is the last thing that happens outside your room. Card-locked lifts are settled before she leaves; they are common enough in the newer towers that the booking message is the right place to mention one.
Why eleven is easy and three is easier
People assume the late hours are the difficult ones. At eleven there are forty people in a lobby. At three there are almost none, and the night porter has seen guests come back at that hour every night of his working life, from delayed flights, from clubs, from a dinner that turned into a longer dinner. Which is why nothing is added to the price after midnight, and why the hours after midnight are an ordinary part of the week here rather than a concession made reluctantly.
The part that belongs to you
Very little. Be in the room. Send the number when you are ready to. Tell the thread what your building asks of visitors, and if you are not sure, ask reception, which answers that question every day. If your hotel runs an evening turndown, skipping it for that night is worth the ten seconds it takes to say so, because a knock at half past nine restarts an evening from zero.
The shape of the practice, including the map and the hours, is set out on the practice page; the district-level detail for the centre sits in the Centrum hotel guide.