Molding planes are in the class of planes called escapement planes, which means the side of the plane is open and the angle of the blade is skewed a bit so that the wood shavings curl out of the side of the plane (see the opening on the plane in the photo below). During the seminar, Roy Underhill used a handheld camera with a light and an excellent zoom lens to follow along while Don ran a plane along a board. He was able to focus in on the cutting edge and show in great detail what has always been theoretical in my mind. I've only seen in drawings the action of the blade forming the shaving and the shaving lifting away from the wood and curling free. It was a great way to show the process up close.
Learning about this and trying out the Clark & Williams planes has inspired me to make my own coffin smoother. That will take lots of research and head-scratching, but I'll try to document the process (not the head-scratching). Along with the planes, the company offers DVDs on plane making and plane use. As with the other exhibitors, it's amazing to see a company's entire product line all in one place and set up to be used.
You can see more of the Clark & Williams line of planes at their website, www.planemaker.com. I highly recommend their section on why 18th Century British planes are the ones they chose to make.