Construct a line segment of length 6.3 cm using ruler and compass.

Steps:

1. Draw a line l and mark a point A on it.

2. Place the pointer end of the compass at the zero mark of the ruler and open the compass so that the pencil end is on the mark indicating 6.3 cm of the ruler.

3. Without changing the opening of the compass, place the pointer end at A and draw an arc to cut line l at the point B.

Hence, AB is the required line segment of length 6.3 cm.