Do you remember when you were little and the dentist used to tell you to use a 'pea-sized amount' of toothpaste to brush your teeth with? Well, I remember hearing these words of dentistry wisdom (teeth) and obediently trying it out when I got home.
There I'd be, stood at the sink with a determined look of concentration on my face, diligently trying to write the letter 'P' on the frustratingly-small surface area of the toothbrush. 'It's just impossible!', I marvelled, wondering how on earth all the grown-ups managed to create such a fiddly letter out of such a cumbersome tube of minty paste. After a while I gave up, and just used a spherical squirt of toothpaste instead. Much easier.