Take a thread and fold it into two halves.
Make a knot at the folded end of the thread.
Now we have two ends.
Insert a wooden bead from one end of the thread.
Now hold both ends together and make a knot.
Now insert another wooden bead, which is of different colour from the other end of the thread. Again hold both ends together and make a knot as shown. Repeat the procedure, until you reach the exact length. Here, we are done.