The following commonly appear at the beginning of a sign:
- 請 (qǐng) ("Please ...")
- 禁止 (jìnzhǐ; "The following is prohibited: ...").
I believe I have seen portrait orientation signs having a single column of characters starting with 禁止 which read from top to bottom (e.g., "No smoking", or something like that). I have never heard of a Chinese sign reading from bottom to top.
The following commonly appear at the end of a sign:
- 樓 lóu (... [storied] building)
- 公司 gōngsī (... company).
I once saw the right side of one of the ubiquitous blue construction trucks bearing two horizontal occurrences of the same company name, almost next to one other. The name read left to right on the passenger door, but read right to left along the truck's flatbed (or vice versa, I don't precisely recall). Kind of unusual to see, e.g.:
司公CBA ABC公司 (where ABC were the Chinese characters of the company name).
This photo from my former Taiwanese language professor has a portrait orientation sign with two columns of characters. Drawing on my previous experience with signs beginning with 禁止 (mentioned above), this is how I scanned it, starting from the top left going down:
- 禁止 (jìnzhǐ) - The following is prohibited:
- 釣魚 (diàoyú) - to fish/fishing (also slang for "to doze off")
- 陽光 (yángguāng) - sunlight, sunshine
- 橋 (qiáo) - bridge (given the as-it-turned-out glamorous nature of the bridge, I suspected that Sunshine, and not the less romantic sounding "Sunlight", Bridge would be the natural English translation, and indeed that turned out to be the official English name)
- blah-上 blah-(shàng) - on blah
Only after hitting the last character did it become clear to me that it should be read starting from the top right going down, i.e.:
No fishing on Sunshine Bridge (the English is in the opposite order of the two 4-character halves of the sentence in Chinese)
Although I can't give the precise grammatical reason why it would be incorrect to read it in the reverse order, I believe it has to do with the 釣魚 verb-object construction which would always be preceded, and never followed, by a modifying place phrase (陽光橋上).
7/3/12: I have since been informed that portrait orientation signs having multiple columns of characters should always be read right to left, as I learned experientially above.
Prior to reading the sign, I initially thought the bridge might have been damaged by some disaster based on the curved metal on the left, and that the sign may have been related to such a change. However, pictures on this other (random) person's blog show that the curved metal is simply part of the bridge's "groovy" architecture.