Having managed a Pub for six years, I grew tired of people saying 'how long is a piece of string?'. So, I trudged off to the Hardware Shop across the road and asked for a piece of string. Well, they stocked a variety of 'string'. I looked at the basic no nonsense string we'll all familiar with and checked its length. Well, it was 100 metres in length. I also checked the other balls of string and, they too were 100 metres in length!.
The proprietor of the hardware shop told me that originally, string was sold by the weight. This was the case for much of his stock i.e. nails and screws.
So, with my new found information, the next time I heard someone say 'how long is a piece of string', I told them 10 ounces !!