3 sentences

1. 船只顺流下行，速度极快。

   chuán​zhī shùn​liú xià​xíng, sù​dù jí kuài.

   The boat moved downstream at a very high speed.

   Source: Dong Chinese Dictionary

2. 古籍中的文字通常是下行书写的。

   gǔ​jí zhōng de wén​zì tōng​cháng shì xià​xíng shū​xiě de.

   Text in ancient books is usually written vertically.

   Source: Dong Chinese Dictionary

3. 他在北京站登上了这趟下行列车。

   tā zài Běi​jīng zhàn dēng​shàng le zhè tàng xià​xíng liè​chē.

   He boarded this outbound train at Beijing Station.

   Source: Dong Chinese Dictionary