"Writing Letters By Hand" joke

Mark and Sharon decide they don't want to discuss sex in front of their 4
and 6 year old children, so they decide to talk in code.

One day Mark is feeling a little bit turned on and says to Katie, "Tell
your mother I would really like to type a letter."

Katie runs off to find her mom. " Mommy, mommy", shouts Katie, "Daddy would
like to type a letter."

Sharon replies slightly sheepishly, "Katie, go and tell your daddy that he
can't type a letter today as there is a red ribbon in the typewriter."

Katie tears off to her father and says, " Daddy, daddy, mommy says you
can't type a letter today as there is a red ribbon in the typewriter."

A few days later Sharon remembers that Mark was a little bit keen on a bit
of nookie and she called Katie, "Katie, tell your daddy that he can type
that letter today."

Katie went off to look for her father and told him, "Daddy, mommy says you
can type the letter today."

"Thats OK, Katie", Mark says, "You can tell your mother that I don't need
the typewriter any more, I wrote the letter by hand."