The proofing of armour is testing

armour Armour (British English) or armor (American English; see spelling differences) is a covering used to protect an object, individual, or vehicle from physical injury or damage, especially direct contact weapons or projectiles during combat, or fr ...

for its defensive ability, most commonly the historical testing of

plate armour Plate armour is a historical type of personal body armour made from bronze, iron, or steel plates, culminating in the iconic suit of armour entirely encasing the wearer. Full plate steel armour developed in Europe during the Late Middle Ages, es ...

and

mail (armour) Chain mail (properly called mail or maille but usually called chain mail or chainmail) is a type of armour consisting of small metal rings linked together in a pattern to form a mesh. It was in common military use between the 3rd century BC and ...

. In the early Middle Ages, armour would be classified by the blows it could withstand, being certified as proof against

sword A sword is an edged, bladed weapon intended for manual cutting or thrusting. Its blade, longer than a knife or dagger, is attached to a hilt and can be straight or curved. A thrusting sword tends to have a straighter blade with a pointed ti ...

axe An axe ( sometimes ax in American English; see spelling differences) is an implement that has been used for millennia to shape, split and cut wood, to harvest timber, as a weapon, and as a ceremonial or heraldic symbol. The axe has many for ...

s, and

arrow An arrow is a fin-stabilized projectile launched by a bow. A typical arrow usually consists of a long, stiff, straight shaft with a weighty (and usually sharp and pointed) arrowhead attached to the front end, multiple fin-like stabilizers c ...

s. As firearms emerged as battlefield weapons, armour would be tested against them, as well, from which came the modern term "bulletproof". In Japan the testing of armor by arrow or a musket ball is called ''tameshi'' with the tested armor being called ''tameshi gusoku''. Helmet and chest armors were tested and many examples of these armors showing the bullet test marks still exist. In the 14th century, Japanese individual scale armor pieces were said to have been tested by arrows before being assembled into an armor.''Secrets of the Samurai: The Martial Arts of Feudal Japan''
Authors Oscar Ratti, Adele Westbrook, Publisher Tuttle Publishing, 1991, P.188

References

* Western plate armour Medieval armour {{Medieval-armour-stub