What is "parrying dagger"

n. A medieval dagger usually wielded with the left hand. It was used primarily for parrying and defense, while the other hand held a longer, single handed sword like a rapier. Also known as a main gauche.

The parrying dagger is a category of small hand-held weapons from the European late Middle Ages and early Renaissance. These weapons were used as off-hand weapons in conjunction with a single-handed sword. As the name implies they were designed to parry, or defend, more effectively than a simple dagger form, typically incorporating a wider guard, and often some other defensive features to better protect the hand, as well. They may also be used for attack if an opportunity arises. The general category includes two more specific kinds of weapon: sword breakers and trident daggers.

The use of this off-hand weapon gradually fell out of favor as sword fighting evolved into the modern sport of fencing. The use of progressively lighter primary weapons such as the small sword, épée, and foil allowed for greater speed as the fencer needed less and less protection for himself as double hits became more and more allowed in the sport fencing.