墙上

qiáng shang de gào shi xiě zhe qǐng wù xī yān

墙上的告示写着“请勿吸烟”。

The notice on the wall says "no smoking".

gē bǎn yīng gāi láo láo dìng zài qiáng shang

搁板应该牢牢钉在墙上。

The shelves should be securely anchored to the wall.