A pencil is a slang word for penis.
A pencil sharpener is a slang word for
vagina.
Pencil shavings is a slang word for cum.
e.g When a
man and a woman have sex, the
man sticks his pencil into the woman's pencil sharpener and they have sex. After a while, pencil shavings explode out of the pencil and into the pencil sharpener.