1. First, prepare a ruler to ensure that the edge of the ruler is flat, without damage or bending.

2. Choose a starting point on the paper and mark it with a pencil or other drawing tools.

This point is where you will start to draw a straight line. Align one side of the ruler with the starting point.

4. Hold the ruler tightly, keep the edge of the ruler aligned with the starting point, draw a straight line along the edge of the ruler with a pencil, and keep your hands steady to make the straight line as straight as possible.

5. If you need to draw a longer straight line, you can move the ruler to a position other than the starting point, realign the edge of the ruler and continue to draw a straight line.