Final answer:
In pencil drawing, blending tools like a shammy and tortillians help create smooth transitions, while a 'gum' or gum eraser is meant to remove material, not blend it.
Step-by-step explanation:
In the context of pencil drawings, blending is a crucial technique used to create gradients and smooth transitions between tones. Certain tools are specifically designed to aid in this process. For example, a shammy, also known as a chamois, is a soft leather cloth that can be used for blending large areas smoothly. Tortillians, which are tight rolls of paper, can be used to blend small details. The term 'gum', however, commonly refers to gum erasers, which lift pencil from the paper rather than blending it. In the case of blending techniques, gum would not be considered useful since its purpose is to remove graphite or charcoal, not to blend it.