Write from the visitor’s starting point
For an evening arrival, “From the street, pass the first door and use the entrance marked 12B” gives the visitor a visible check. Try the route once after dark. If the number is hard to see, arrange a meeting point instead of giving increasingly complex directions. Use the travel direction the visitor will actually take. “Left of the building” changes meaning depending on where they stand. A named street and an entrance number survive that ambiguity.
Walk the route under similar conditions
Try arriving after dark from the agreed bus stop or parking area. Is the sign lit? Does the visible entrance close at a particular hour? Can the visitor read the number without stepping into traffic? Change the instructions based on what you observe and offer another route if the path is inaccessible.
Provide a fallback that respects privacy
Agree on a staffed or well-lit meeting point if the entrance is difficult to identify. Give a contact route suitable for that visit. Do not put a permanent access code or a hidden-key location into a widely forwarded set of directions simply to make the final step easier.