lead in pencil 

it is said of people of little strength, character or resolve. also said about men who can't get an erection during sex.

I slept with Roger last night. He couldn't get it up. he's got no lead in pencil (or no lead in his pencil).

lead in pencil by Yoova September 17, 2006

Putting Lead In Your Pencil 

From the Journal Of The Royal Society Of Medicine. To insert a foreign object into ones Urethra for sexual pleasure especially during masturbation. Damn Doctors U got scary black humour.

A 62-year-old man was referred to us from a nursing home by staff concerned that he had apparently passed a small household (AAA size) battery per urethra. The patient was in pain with difficulty in passing urine. Relevant in his past medical history was that one year previously we had endoscopically removed a pen lid from his bulbar urethra.

An X-ray of his pelvis revealed what appeared to be two dense foreign bodies in his urethra. Urethroscopy revealed two AAA size household batteries lodged in his bulbar urethra. On further questioning at discharge, the patient admitted to inserting three AAA sized batteries into his urethra for sexual gratification during masturbation four weeks earlier. The Doctors decided to call it putting lead in your pencil, the age old euphemism for sexual vigour and erections.

Putting Lead In Your Pencil by Mengele's lab rat January 12, 2012

no lead in their pencil 

A slang comment relating to cowardly people, those with no backbone, lacking courage or character. It also means the inability to gain an erection during sex.

'Ironically the French terrorists who attacked Charlie Hebdo had no lead in their pencils. Also, it is rumoured that they had no lead in their pencils'

no lead in their pencil by ZJ3EF January 8, 2015