凵 is also the 20th indexing component in the Table of Indexing Chinese Character Components predominantly adopted by Simplified Chinese dictionaries published in mainland China.

In the Kangxi Dictionary, there are 23 characters (out of 49,030) to be found under this radical.

As for the similar radicals 22 匚 and 13 冂, the name of radical 17 is purely descriptive of its shape, 下三框 "lower three-sided frame".

In combination, it historically takes meanings such as "open mouth", "box", "frame", "hole" or "receptacle".

Also derived from the radical are the Simplified Chinese characters including 击 "to hit", without any historical connection to the radical.