The casing with four holes can be penetrated as follows:

1. Put this shell in order first, make this shell into a stack, and then clamp it and fix it.

2. Make four symmetrical marks on the shell from the horizontal direction with a ruler.

3. Thread the needle into these marks, and finally make one hole in the middle of these holes ring-shaped, and the others are thread ends.

4. Hold the thread ends on both sides by hand, and cross-tie and fix them.

Finally, use your own scissors to cut off the excess part of the thread.

The above steps are for reference only, and the operation method can be adjusted according to the actual situation.