put lead in (one's) pencil

Of a man, to increase, enhance, or restore one's sexual ability or vigor. Following this six-step program will put lead in your pencil, guaranteed. The only real way to put lead in your pencil is to eat well, exercise regularly, and have self-confidence.

Enhance or restore sexual vigor, as in Try one of these hot peppers; that'll put lead in your pencil. This phrase, a euphemism for causing an erection, is considered far more vulgar than the contemporary synonym put hair on one's chest, alluding to a secondary male sex characteristic. [Colloquial; c. 1900]

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.