During the actual production process, a dozen steps are taken, such as measuring the dimensions, cutting fabrics, constructing the frame and making the paste, the interior and the clasp.

"When receiving a cultural relic, the first step is to measure its basic dimensions and draw a basic model," Gao says.

A container generally has to be one-third larger than the item's dimensions, which should be precisely measured.

"You need to ensure that, when the item is put inside, it will fit perfectly and be tightly sealed," he says.

"For example, a container for a porcelain bowl can be turned upside down without the bowl falling out. Even if you throw it 10 meters with the lid closed, and the box breaks, the bowl shouldn't crack."

When an item features an irregular shape, data on various parts should be obtained and then a related model diagram needs to be drawn.

For fabrics, Song brocade, which has a gorgeous color and a soft texture, is commonly used.

"The design must be based on the characteristics of the item it will house, using luxurious and auspicious patterns that render a harmonious effect inside and out," Gao says, adding that traditional cutting techniques are also applied.

For example, he made a container with a mountain and stone background for a butterfly-patterned hairpin.

"The hairpin can be inserted in a slot in the background, so the chances of hands touching it can be reduced and the whole thing creates a whole picture," he explains.