A few days before Mid-Autumn Festival, the elderly in the family start preparing mooncakes. They mix the dough, adjust the filling, wrap it up, press it into the mold, and then knock it out after pressing it firmly with their palms. Only then is a mooncake fully formed. Whether the pattern is clear or not depends entirely on whether the pressing is sufficient. The children standing by find it troublesome and ask why they can't just pinch it loosely. The elderly, without raising their heads, respond that if it's not pressed firmly, it won't hold its shape.

In a nutshell, it's about mooncakes, but what's hidden within is an old principle that has been used for thousands of years. This principle exists in the dim sum box, and it's also buried beneath the railway ballast.

Mooncakes, when it comes to quality, the word "solid" is the key. The skin and filling must be tightly adhered, and the mold pressed into place, so that there is no extra space inside. Solid mooncakes feel heavy in the hand, retain their shape even after being stored for a few days, and the patterns remain intact. If they are loose and floppy, with the skin being the skin and the filling being the filling, air can easily sneak into the gaps, and it won't take long for the mooncake to lose its air and become soft on the outside and bland on the inside. Mid-Autumn mooncakes should be left untouched until after the 15th day of the lunar month, relying solely on that initial press.

The number of people who give mooncakes during the Mid-Autumn Festival is also well-known. The gift box bumps along the way in the bag, and when it is opened at the relative's house, the mooncakes that are packed tightly are still neat and intact. They can withstand being displayed and bumping, and this dignity is given by the initial pressing.

Wood and mooncakes are a world apart, yet their fears are similar: fear of emptiness. Wood comes from trees, with fibers arranged closely together, appearing airtight. However, between the fibers, there are naturally existing gaps. These gaps are so tiny that they are invisible, and they remain silent in ordinary times. But in the wild, they become a different story. Water flows through the gaps, insects gnaw through them, and fungi make their homes there. Wood cannot fend off these threats on its own, and anyone can enter and take up residence. As time goes by, the inside is hollowed out.

So, when oil is soaked into a wooden tank, the aim is also to achieve solidity. The oil flows along the fiber seams and fills up the gaps. Where the oil settles, water cannot enter, insects cannot gnaw, and fungi cannot take root. The more the gaps are filled, the denser the wood becomes. A thoroughly soaked sleeper is full from the outside to the inside. No matter how many years it is laid on the track, there is no space left for foreign objects inside.

This piece is full and can withstand rough handling. When the sleepers leave the factory, they need to be loaded onto trucks, and when they arrive at the construction site, they need to be unloaded. After being laid on the track, they are subjected to daily wear and tear. Hollow and loose materials would lose their shape after just a few trips. However, the oil-impregnated wood is not afraid of this. It can withstand being pressed and worn, and it is a unified whole inside and out, which cannot be dismantled.

One is pressing molds on a cutting board, and the other is eating oil in a big jar. These two professions have nothing to do with each other, but they both emphasize the same word. "Solid", not in the sense of being dead and heavy, but rather not having any extra space inside. Without space, outside things cannot penetrate. The older generation also lived by this principle. The rice jar should be pressed solid, and the wall cracks should be filled tightly. Solid things can withstand being stored and can withstand being looked at.

This sincerity is only evident on the track. Around Mid-Autumn Festival, the railway is at its busiest, with trains coming and going one after another, busier than usual. The sleepers on the main line are constantly being pressed, those in the mining tunnels are soaked in moisture, and those on the bridges are exposed to the wind and sun, all supporting their respective positions. While people celebrate the festival, they also celebrate, but their celebration is a peaceful one, relying on the solidity they gained when they were soaked in oil. This confidence was built up mouthful by mouthful in the tank back then.

You sit in the carriage on your way home, watching the black wooden poles outside the window recede one by one, supporting the two steel rails steadily section by section. Only when the train runs steadily can you enjoy watching the moon rise. This stability is not free, but the result of taking one mouthful after another of oil in the tank back then.

Speaking of which, Mid-Autumn Festival is upon us. May your journey home be smooth and uneventful, may the mooncakes on the table be plump and delicious, and may everyone who gathers together be filled with genuine joy. Qingdao Tiehan wishes you a happy Mid-Autumn Festival, family reunion, and a perfect circle of people and the moon.