First World War
Soldiers in the trenches in 1915 did not have factory made hand grenades in large numbers, and improvised devices were by putting gun-cotton and scrap metal in empty jam tims. "Jampots" were crude; Desmond Morton describes one method of making them in When Your Number's Up:
Private W.S. Lighthall of the Royal Canadian Dragoons was taught to empty the jam tin, line it with burlap and an inner lining of mud. "Insert old nails and broken metal, centre a primer of gun cotton and make a small hole for the copper detonator and a short length of fuse. Cramp (sic) the copper with your teeth (dangerous). Apply more mud to hold the fuse in position, tie burlap around the fuse, light it with a cigarette, and wait five seconds for the explosion, preferably at a distance."