The middle inside
The character has Cloth, Bird, Field. What is the meaning of the character?
《象形字典》（Dictionary of Pictography) explains that people use cloth to capture the bird in the field, the cloth can cover the bird to stop it flying away.
Some people don't agree with this explanation, they think that the character means that the bird captured and covered by cloth try to exert itself to fly away, which shows the meaning of Exert.
The interesting thing in this field, many unknowns and many disputes, not many standard answers.
The big seal script of character Exert is
Similar to bronze script.
The small seal script of the character is
The outside Cloth become bent 土 (soil) on the top, the middle Bird, and bottom Field keep the same.
The clerical script of the character is
The top 土 become 大 （big), the middle and bottom keep the same.
The traditional sone typeface is
Similar to the clerical script.
The simplified song typeface is
The middle 隹 （bird) disappeared, lost the most important part.
Its Pinyin is Fen4.