Where does the military apply for a patent?

Friction magnetization of sewing needle on magnet. Put a piece of hard paper on a bowl of water, put the magnetized needle on the paper, and then push the paper into the water, and the needle will float on the water and point to the south. If the pointer sinks, try a few more times. Its price does not exceed 50 cents.

Respondent: Sheng Honghao-Tong Sheng Yi Ji 2- 1 1 19:43.

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Support this comrade, hehe! But it's better if I teach you. Just take the needle out in wax water and put it in water!

In addition, the needle can mend clothes when it is not a compass, and it can also prevent the satyr from stabbing him!

Candles can be used for lighting and burning in the wild.

Ha ha laugh