Hexagram 21, Shì Kè (Biting Through): Line 4
噬嗑卦九四 · 火雷噬嗑 · 中文版
九四：噬干胏，得金矢，利艰贞，吉。
The line (Legge)
The fourth NINE, undivided, shows one gnawing the flesh dried on the bone, and getting the pledges of money and arrows. It will be advantageous to him to realise the difficulty of his task and be firm,--in which case there will be good fortune.
Small Image commentary
'It will be advantageous to him to realise the difficulty of his task and be firm, in which case there will be good fortune:' - his light has not yet been sufficiently displayed.
象曰：利艰贞吉，未光也。
In plain words
Biting into dried meat on the bone and finding a metal arrowhead; it is favourable to be steadfast in hardship: good fortune. The arrowhead stands for firmness and straightness. The fourth line tackles hard matters with strength and must hold to that, persisting through difficulty. The Small Image says its light has not yet spread.
Applying it to your situation
If you are gnawing on a hard problem, this line suggests staying firm and straight and persisting. What do you most need to hold on to in this?
Position
A solid (yang) line in the fourth place, which is a yin (even) place, so it is not in its proper place. Its partner is line 1; both are yang, so they do not respond.
If this line moves
With this line moving alone, Shì Kè changes into Hexagram 27 Yí (Nourishment). The Jiaoshi Yilin verse for this change (Chinese): 焦氏易林·噬嗑之颐.
A recorded case from Takashima
Shi He to Yi: how a business dispute will end: An acquaintance caught up in a major business dispute received the fourth line of Shi He, "biting dried meat on the bone; finding a bronze arrow; persevering in hardship is good". Takashima said the other side was tough and difficult, a firm and upright person would be needed to settle it, and though slow it would end.
The hexagram
Hexagram 21 Shì Kè (Biting Through). The Judgment: Shi He indicates successful progress (in the condition of things which it supposes). It will be advantageous to use legal constraints.
Previous: Line 3 · Next: Line 5
English text: James Legge, The Yi King (Sacred Books of the East, vol. 16, 1882), public domain, as transcribed by the Chinese Text Project. Chinese: the received text. Offered for study and reflection, not as prediction. Plain-English readings and position notes by this site.