Push dagger

A push dagger (alternately known as a punch dagger, punch knife, push knife or, less often, a push dirk) is a short-bladed dagger with a "T" handle designed to be grasped and held in a closed-fist hand so that the blade protrudes from the front of the fist, either between the index and middle fingers or between the two central fingers, when the grip and blade are symmetrical.

It originated as a close-combat weapon for civilians in the early 19th century, and also saw some use in the trench warfare of World War I.