Front: "Don single jacking, Glengarry mine" MacDonald knight using a hammer and drilling steel to create holes in rock. From the USDA Forest Service website: "Single jacking involves an individual holding a drilling steel in one hand and hitting it with a hammer held in the other. The single jacks have 3- or 4-pound heads and 10-inch handles. The short handle helps you place blows accurately and resists breaking better than longer handles. Engineer's...