Friction is reduced/increased through use of roller.

Explanation

### Step-by-Step Solution:

1. **Understanding Friction**: Friction is a force that opposes the motion of an object. It arises due to the irregularities present on the surfaces in contact.

2. **Analyzing the Surface**: When we look at a surface closely, we can see that it has various irregularities, such as bumps and valleys. These irregularities contribute to the overall roughness of the surface.

3. **Introducing the Roller**: When a roller is placed on a flat surface, it rolls over the surface rather than sliding. The roller has a cylindrical shape that allows it to smooth out the surface as it moves.

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