"A horse's leg is like a table"
The speaker was a professor of veterinary medicine and he was describing at great length how to set medio-lateral hoof balance by using a T-square, like this.
It seemed over-simplistic to me at the time, for several reasons - not least because setting foot balance this way doesn't factor in what happens when the horse moves and takes no account of how the foot is landing.
But the biggest problem - as you can see the minute you pick up a T-square and try placing it on several different horses - is that it only works if you have a horse with a completely straight leg.
If you use a T-square to check balance on a horse with a leg that is not perfectly straight you end up with a T square which is also angled. According to the T square (and the professor) you then need to do some pretty invasive shoeing or trimming to ensure that you get back to 90 degrees which - of course - will make the horse sore and impair its movement. Its another example of the problems of imposing our ideas of symmetry instead of listening to the horse.
However, if there is one thing I've learnt its that there is no use trying to argue people out of their deeply held beliefs. So nowadays if someone tells me a horse's leg is like a table I just smile and concur with the veterinary professor - simply adding the caveat that there is more than one sort of table...