I didn't know what one of these was either, until I was asked to make one.
Actually they are surprisingly comfortable, the idea is to kneel and place the stool between your legs, resulting in your body
weight passing through the stool rather than squash your legs.
The curved bottom of the 'T' allows the seat to sit at any angle to the floor, so that it sits at a comfortable
angle when sat on - infinitely adjustable to any body shape would be the marketing speak I'm sure.
