From Rhizome Artbase

Read all the instructions and study the drawings before beginning work. (Most families have found it helpful first to read the instructions aloud and then to discuss problems and work assignments.) When digging earth that is too firm to shovel without first breaking it up, start picking (or breaking with a shovel) in a line across the center of the trench. Next, shovel out a narrow trench 6 or 8 in. deep all the way across the width of the trench. Then with pick or shovel break off row after row of earth all the way across the width of the trench, as illustrated.