to send over to Fritz with Tommy's compliments.

A piece of wood about four inches long and two inches wide had been
issued. This was to be strapped on the left forearm by means of two
leather straps and was like the side of a match box; it was called a
"striker." There was a tip like the head of a match on the fuse of the
bomb. To ignite the fuse, you had to rub it on the "striker," just the
same as striking a match. The fuse was timed to five seconds or
longer. Some of the fuses issued in those days would burn down in a
second or two, while others would "sizz" for a week before exploding.
Back in Blighty the munition workers weren't quite up to snuff, the
way they are now. If the fuse took a notion to burn too quickly, they
generally buried the bombmaker next day. So making bombs could not be
called a "cushy" or safe job.

After making several bombs, the Professor instructs the platoon in
throwing them. He takes a "jam tin" from the fire step, trembling a
little, because it is nervous work, especially when new at it, lights
the fuse on his striker. The fuse begins to "sizz" and sputter and a
spiral of smoke, like that from a smouldering fag, rises from it. The
platoon splits in two and ducks around the traverse nearest to them.
They don't like the looks and sound of the burning fuse. When that
fuse begins to smoke and "sizz" you want to say good-bye to it as soon
as possible, so Tommy with all his might chucks it over the top and
crouches against the parapet, waiting for the explosion.

Lots of times in bombing, the "Jam tin" would be picked up by the
Germans, before it exploded and thrown back at Tommy with dire
results.