The German rifle grenade key (Gewehrgranatenschlüssel)
 
 During the Second World War, the German army developed various tools to make their infantry weapons more versatile. One of these was the Gewehrgranatenschlüssel , or rifle grenade key . This specific tool was used in conjunction with the Gewehrgranatgerät (rifle grenade device), an attachment mounted on the barrel of the standard infantry rifle – usually the Karabiner 98k – to fire rifle grenades.
 
 Function of the grenade key
 
 The rifle grenade wrench was an essential tool for the maintenance, disassembly, and assembly of the rifle grenade device. The device itself consisted of multiple metal parts that had to be cleaned and adjusted regularly, especially after repeated use with powerful grenades.