3 sentences

1. 他迈过高高的木门槛，进了正屋。

   tā mài​guò gāo gāo de mù mén​kǎn, jìn le zhèng​wū.

   He stepped over the high wooden threshold and entered the main room.

   Source: Dong Chinese Dictionary

2. 他在门槛上划了一个深深的记，用来观察水位的变化。

   tā zài mén​kǎn shàng huá le yī gè shēn​shēn de jì, yòng​lái guān​chá shuǐ​wèi de biàn​huà.

   He carved a deep mark on the threshold to observe the changes in the water level.

   Source: Dong Chinese Dictionary

3. 要是不懂其中的门槛，买东西很容易吃亏。

   yào​shi bù dǒng qí​zhōng de mén​kǎn, mǎi dōng​xi hěn róng​yì chī​kuī.

   If you don't know the ropes, it's easy to get ripped off when buying things.

   Source: Dong Chinese Dictionary