A rookie skydiver is descending on his first solo jump, the earth is fast rushing up to meet him. He pulls his ripcord, but nothing happens.
He reaches for his reserve, pulls the cord, and again, nothing happens.
Luckily he sees a man passing him going in the opposite direction.
"Excuse me" shouts the Skydiver, "Do you know anything about parachutes?"
"No, sorry" says the other man, "do you know anything about gas boilers?"
(Copyright "The Comedians", 1975)