3 sentences

1. 他在文件的底部签名。

   tā zài wén​jiàn de dǐ​bù qiān​míng.

   He signed his name at the bottom of the document.

   Source: Dong Chinese Dictionary

2. 壁炉底部的灰堆得很高，需要清理一下。

   bì​lú dǐ​bù de huī duī de hěn gāo, xū​yào qīng​lǐ yī​xià.

   Ash has piled up high at the bottom of the fireplace and needs to be cleaned up.

   Source: Dong Chinese Dictionary

3. 高年级的课本都放在左边书架最底部。

   gāo nián​jí de kè​běn dōu fàng zài zuǒ​bian shū​jià zuì dǐ​bù.

   All the senior textbooks are on the bottom shelf on the left.

   Source: OpenSubtitles