If someone says that something puts lead in a man's pencil, they are suggesting humorously that it improves his sexual ability. Note: Lead is a very heavy metal. Steve chewed the tobacco and spat a brown spot into the snow. `Puts lead in your pencil,' he said. Note: You can also say that someone has lead in their pencil, to praise their sexual ability. He'd been blessed with amazing stamina and a lot of lead in his pencil. Note: The lead in a pencil is the part in the centre which makes a mark on paper.