From Robinson Crusoe

There is strength in numbers.

Even though the number of people on the island has only increased from one person to three, the effect produced is far greater than 1+1+1.

Reasonable division of labor can maximize the areas of expertise of the three people and thus improve work efficiency.

Chen Zhou was busy and busy. By May 5, the day of the 18th mysterious arrival, he had completed most of the items in the schedule, leaving only the watchtower and beacon tower on the mountainside to be built.

……

Worried about a sudden attack from the natives of the large tribe.

Every Saturday before going out to herd sheep, Chen Zhou would remind him to be smart and observe whether there were any unusual conditions on the northeast corner of the beach. If he spotted any strange canoes approaching, he should come back and report immediately.

Although Saturday is not as smart as Sunday, he is still very steady and reliable. Once he promises to do something, he rarely makes mistakes. He can be said to be a person who can make people feel at ease.

At least based on Chen Zhou's understanding of the two, it would be much more reliable to let them go to observe the beach on Saturday than on Sunday.

……

There's nothing new about the recent rewards.

On May 5, when Chen Zhou went to the beach, he thought he was going to pick up another useless item, but unexpectedly he saw the long-lost blue square in the center of the wood and stone wall.

"Wow! New decryption?"

Even though he was tortured enough by the puzzles sent by the Space-Time Administration in the past, Chen Zhou sometimes felt bored when there were no new challenges for a few months.

Maybe this is a kind of "Stockholm syndrome"! He always thinks so.

Sometimes, when life is too good, all kinds of troubles may arise. It may not be a bad thing to relive the feeling of burning your brain and the frustration of not being able to solve the puzzle.

……

Let the Saturdays and Sundays that come with us tidy up the wood and stone walls—

Now Chen Zhou no longer needs to do this work. From sorting to stacking, the two natives can complete it independently, saving Chen Zhou a lot of trouble.

Walking to the middle of the sand, Chen Zhou took down the blue square box hanging in the air and began to examine its structure.

Unlike the first puzzle, the safe, the second puzzle, the "holy sword", and the third puzzle, the "pure blue hell", the solution to this puzzle does not seem to be an exhaustive method.

……

In Chen Zhou's hand was a small lock with a peculiar shape.

The surface of the lock is extremely smooth, with only one keyhole left. It seems easy to solve the puzzle - all you need to do is find a suitable key for the lock.

But the key to the problem lies in the material of the lock.

As far as Chen Zhou knows, most modern locksmiths make keys by directly removing the lock core and then making the key by observing the shape, height and arrangement order of the lock teeth.

Or you can remove the aluminum seal behind the lock teeth, take out only the spring and teeth, record the spacing and height of the teeth, and thus determine the tooth shape of the key.

After making the key blank, insert the key into the lock cylinder and adjust the tooth height little by little to make a qualified key.

Both methods have a common premise, which is that the lock can be disassembled.

However, the small cube in Chen Zhou's hand is different from modern locks. The material used to make it is indestructible, and there are no screws or even cracks on the surface of the cube. It is a pipe dream to want to take it apart.

……

"Then we can only try slowly by observing and guessing the internal structure of the lock core..."

Chen Zhou muttered to himself, knowing that he had no ability to destroy this material that was beyond human cognition.

He raised the square lock and squinted his eyes to look inside the keyhole.

The blue material emits a faint glow, and you can vaguely see the uneven marbles and shrapnel in the keyhole, but it is very blurry. It would be quite difficult to use it to make a suitable key.

"If we make a key blank out of softer gold, silver or lead, insert it into the keyhole, twist it forcefully, and apply pressure to the key blank, thus leaving an imprint, would it be easier to determine the tooth shape?"

The new puzzles were much more interesting than the boring jigsaw puzzles, plus Chen Zhou was eager to get richer rewards.

While he was still standing in the sand, his brain was already active.

……

After spending Saturday and Sunday carefully arranging and building the wooden and stone walls, Chen Zhou returned to the cave without stopping. He put aside other work and began to concentrate on studying how to unscrew the lock.

……

Chen Zhou didn't know that his way of unlocking the door was a professional high-level technique among locksmiths, called "secret key dubbing" or "impression key dubbing".

This technique sounds simple, but it is difficult to implement.

The locksmith who makes the keys must have a very good understanding of locks and needs to have a delicate sense of hand.

When the key blank is inserted into the keyhole and pressure is applied in the direction of the marble, the marble will be touched and produce subtle changes. As a locksmith, you can sense this change and make a key more quickly.

Moreover, the key blank itself is relatively thin and light, so you should not use excessive force during the turning process, otherwise the key blank will be greatly deformed or even break in the keyhole, which will not be worth the loss.

Even an experienced locksmith still needs to use some unconventional methods to make keys secretly.

For example, use a light to illuminate the inside of the keyhole, or illuminate the mark on the key blank, so that you can more clearly see how many groups of marbles there are in the lock, how many concave teeth there are, and how many convex teeth there are.

Or use a magnifying glass.

There is even a method of using smoke to blacken the keyhole, then inserting the key blank into the keyhole, and guessing the approximate shape of the key based on the marks left by the smoke on the blank.

And Chen Zhou obviously didn't know any of these methods.

...After returning to the cave, he walked straight into the forging room and took out a small piece of lead plate from the material area.

If it weren't for this sudden puzzle, his recent plan, in addition to building watchtowers and beacon towers, would have been to study the use of the lost wax method to cast lead Minié bullets, in order to prepare for new firearms in advance.

Because of this, there were many more lead plates in the forging room, and even the graphite crucible that had been stored on the fire wall was moved here.

……

The hardness of lead is not high. Chen Zhou measured the size of the key hole, drew the specific size on the lead plate, picked up a hacksaw, and quickly cut off a piece of "key blank" from the lead plate.

Then he took out the grindstone and smoothed out the uneven saw marks on the surface of the blank, making it smoother and more flat to facilitate checking the imprint.

After completion, the entire key blank is in the shape of a regular long strip.

It is slightly thinner than the keyhole for easier insertion.

Knowing very well that this puzzle would not be easily solved, Chen Zhou carefully observed all sides of the lead strip before inserting the key blank, and drew on paper several marks currently remaining on its surface to prevent them from affecting his judgment and causing mistakes later.

After finishing the preparations, Chen Zhou decisively inserted the key blank into the keyhole.

……

The result was frustrating; he couldn't even fully insert the key blank, let alone turn it to understand the tooth pattern in the hole.

Looking at the key blank that had only the first centimeter inserted into the keyhole, Chen Zhou pulled it out helplessly, and then based on the newly added, pitifully small marks on it, he guessed what to do next.

……

After repeated attempts and guesses, it was already late at night.

Looking at the key blank that was filed as if it had been chewed by a dog, Chen Zhou placed the lock in his hand on the table. He felt an endless fatigue surge up and almost drowned him.

"too difficult!

Damn, is this a puzzle that a human could come up with?

Unless I have an endoscope, how many times do I have to try before I find the right answer?"

After practice, Chen Zhou finally realized that making this key was not only not easy, but also ten or a hundred times more difficult than he had imagined.

Even if he had a general understanding of the height distribution of the teeth, grinding the key blank was not an easy job.

……

If you want to complete this job, you either need to find a master who has been engaged in the locksmith industry for many years, who can keenly sense the physical feedback of the internal components of the lock core, and who can reversely deduce the key tooth shape and manually correct it based on the imprints and resistance, to help.

Or you have to take an unconventional approach and come up with something unique and creative.

Naturally, the old locksmith couldn't be found, so Chen Zhou could only find a shortcut.

Not to mention, he happened to be studying the use of the lost wax method to cast Minié bullets recently, and he actually came up with a bold idea to solve the problem -

Melt the wax and pour it into the keyhole, then stick a key grip at the root of the keyhole wax blank, and finally use high-temperature resistant white clay to make a mold, wrap the wax key blank in it, and leave a small hole to pour in the molten lead.

If successful, you will obtain a lead key that is very close to the inner teeth of the lock.

Then just a few tweaks are needed to solve the puzzle.

……

After careful consideration, Chen Zhou felt that his bold idea was highly feasible.

However, before he began his attempt, he had to conduct a series of tests on the material of the small cube to prevent the cast lead key from getting stuck in the keyhole and unable to be taken out, which would make the puzzle impossible to solve forever.

Since coming up with the unique idea on the evening of May 5, Chen Zhou has spared no effort in testing the properties of the material used to make the small cubes.

He found that this light blue material had the following characteristics:
1. It is indestructible. Its hardness is at least at the level of diamond, and it has excellent toughness. With Chen Zhou's current conditions, it is impossible to damage it through violence.

2. Delicate and smooth, the surface of the block looks like it was cut by time and space, so smooth that you can't even feel any resistance when you lightly rub it with your finger.

Influenced by this characteristic, Chen Zhou also found that the block would not stick to any substance, even if fish bladder glue was applied on it.

As for the last characteristic, it is excellent thermal conductivity and unknown melting point.

If you insert a thin piece of lead into the keyhole, and then put the small block into a forge and calcine it at high temperature.

When the thin lead strip in the keyhole melts due to the high temperature, the block will not deform at all, and its color will remain light blue from beginning to end, which is quite eye-catching in the flames.

These three characteristics give Chen Zhou enough confidence.

Indestructible means that the block will not be damaged by his daring attempts.

The fact that it is smooth and not adhered to other substances means that the lead key blank poured into the keyhole will not be completely locked in the hole and can most likely be pulled out directly.

The last point represents a very high tolerance for errors.

Even if the lead key blank gets stuck in the hole, there is no need to worry. Just put the block with the key hole facing down into the crucible and calcine it with a strong fire. When the temperature in the crucible reaches the melting point of lead, the key blank will naturally turn into lead liquid and flow out of the key hole.

This way, he has unlimited opportunities for trial and error.

……

Make a complete plan and take a night off.

Rehearse this in your mind repeatedly to make sure that your attempt will not have any serious consequences.

On May 5, Chen Zhou officially began to try his unique method of solving problems. (End of this chapter)