Power's Scale of Roundness
Particle sampling can be divided into two large components, namely particle size and particle shape. Both are equally important and it is expected that any project involving particle sampling has to include both types in its scope of work. Both have their respective tools and scales of measurement: for particle size, it is the pebbleometer and the phi scale; and for particle shape, it is the stoneboard, the Cailleux Roundness Index and the Power's Scale of Roundness.
All you have to do while using the Powers' Scale of Roundness is to take any particle you want and compare it with the pictures shown on the chart and make your own conclusions from thereon. Repeat this for any number of particles (easy as all you're doing is observing) you want and note the number of particles that fall into each category and in a wink, you'll have achieved a conclusion on the roundness of particles at your chosen site.