How do you use a number line to find an equivalent fraction?

Here is an example. Divide the interval from 0 to 1 into two equal parts. Each parts is then 1/2. Next, perhaps below or above the first divisions, divide the same interval into four equal parts. Each of the pieces is 1/4. You can now clearly see that 1/2 is equivalent from 2/4 - i.e., both are the same distance from zero.

Note that methods that rely only on calculations are easier to use - but the number line can help, initially, to visualize the concept of equivalent fractions.