this is the one the lee enfeld uses.
Cup-Type Rifle GrenadeThe cup-type launcher replaced the rod-type rifle-grenade during World War One. This soup-can shaped launcher is attached to a rifle's muzzle. The cup-type launcher could launch a standard hand-grenade or a purpose built cup-type grenade. To use
First
Insert a grenade into the cup launcher. When using a standard hand-grenade remove the safety pin, the cup holds the safety-spoon in place until launched.
Second
Insert a special blank cartridge into the rifles chamber.
Third
Place the butt-stock of the rifle on the ground and fire from this position.
quite inefficient and it seems this is the one placed on the ground.
heck, if you look up a guy using just a tennis ball on youtube, he places it on the ground to fire.