Apparently he was in possession of a large weapon but tried to conceal it

https://www.femalefirst.co.uk/music/musicnews/Frank+Sinatra-86979.html#:~:text=The%20journalist%20spent%20five%20years,he%20had%20a%20big%20penis.&text=%22But%20oddly%20enough%2C%20it%20was,Sinatra%20was%20self%2Dconscious%20about.

Frank Sinatra attempted to cover up the fact he was well hung - because he thought the size of his manhood was one of many negatives about his body, according to the late star's new biographer James Kaplan.

The journalist spent five years researching his acclaimed new tome, Frank - The Voice, and reveals Sinatra wasn't like most men, who revelled inthe fact he had a big penis.