Qi Ji Guang's Gang Rou Pai (剛柔牌)

Unlike contemporary European powers where the use of firearms stimulated the development and refinement of plate armour, the Chinese never developed plate armour in the first place. They instead turned to the millennia-old philosophy of "conquering the unyielding with the yielding" for a solution.

Ruan Bi (軟壁, 'Soft wall')

Ruan Bi, from 'Ji Xiao Xin Shu (《紀效新書》)'.

Ruan Bi was an improvised defensive structure or mantlet against small caliber firearms. It was a wooden frame covered with old cotton blanket, and could be further reinforced with wooden planks.

Gang Rou Pai (剛柔牌, roughly translated as 'Shield of inflexibility and yielding')

"According to Goodnight, Commanche shields, made from two layers of the toughest rawhide from the neck of a buffalo and hardened in fire, were almost invulnerable to bullets when stuffed with paper."
— Empire of the Summer Moon by S. C. Gwyne, describing Commanche shields with striking similarities to Gang Rou Pai.

Details on the layering of Gang Rou Pai from 'Ji Xiao Xin Shu (《紀效新書》)'. This shield was a military secret, and thus did not have a drawing.

While an effective makeshift mantlet, the defensive properties of Ruan Bi still left something to be desired. Realising its shortcoming, Ming commander Qi Ji Guang (戚繼光) developed the Gang Rou Pai, which was a more effective version of Ruan Bi. Gang Rou Pai was constructed on similar principles as modern composite armour: by layering different materials together to make a stronger composite. 

The outermost layer of a Gang Rou Pai consisted of cowhide nailed onto a wooden frame at both sides. A waterproofed cloth bag, stuffed with three jin of fine silk wadding, was sandwiched between the cow hides, and a layer of crumbled paper balls occupied the innermost part. These layers were fixed together with bamboo nails, and the wooden frame would be covered with yet another bag stuffed with silk floss as well. After that, the entire shield would be painted over in ash paint.

Gang Rou Pai was proof to arquebus shots from up to forty paces away. However, it began to lose effectiveness at thirty paces.