Once you have caught the fish, you forget the bamboo trap.
Tips
history
Not used in modern Chinese as a free word. It survives in the Zhuangzi saying 得鱼忘筌 — once the goal is reached, the means can be set aside; the trap stands for any tool or method.
memory
Bamboo ⺮ over 全 (whole): a woven bamboo basket that catches the fish whole — a fish trap.