Badger and Normal

Badger & Normal is an Ankh-Morpork pyrotechnics firm manufacturing signal flares and rockets for the military and industry, and presumably artistic fireworks. Being in a business fraught with some risk, they obviously employ members of the Guild of Lawyers to create carefully worded instructions for their products. The shell Sam uses to dispatch Wolfgang von Überwald is labelled "Mortar Flare (Red). Light Fuse. Do Not Place in Mouth."

Some of the silly places people have inserted fireworks

There's always one, isn't there... Private Eye once reported on the case of the young man, fuelled by drink and bravado, who chose to insert the base of a Roman Candle into a most ill-advised place. He dropped his trousers, bent over, inserted lit firework, and clenched hard...

...a hospital spokesman later said his condition was satisfactory, although loss of a testicle and a lower length of bowel necessitating a colostomy insertion would remain a lifelong problem.

There may well be a need for those warnings...