A Dirk is a very sharp, dagger-like knife with either a single or double-edge construction. The Sgian Dubh is typically smaller. Historically, the Dirk was worn on the belt, and the Sgian Dubh would be worn in a sock. Both could be considered daggers, but the Dirk is slightly larger and meant to be more dangerous. The Dirk is a weapon while a Sgian Dubh might be regarded as the last defense or for eating.