About 20 years ago I had the good fortune to meet one of the country's best stock makers. who gave me a sanding block that I've used ever since and which has made a significant contribution to the quality of my work. The material is solid cork. It's rectangular, 3 1/2 x 2 1/4". A cross section is the shape of an airplane wing with a leading edge radius of1/2" and a trailing edge radius of 1/4". The top surface is curved, and the bottom flat. The shape makes it versatile, and the material makes it durable with just the slightest hint of resilience. Softer or harder material would not work as well. I don't know a source for these. but you can make your own.
