Measure the length and width for the tie. This is the distance from the shirt collar to the waist line of your toddler. The width of the tie should be almost the same width of your toddler's coat lapel, if he is wearing a coat as well.
Open the seam at the back of the adult tie using a sewing threader and spread the tie flat. Mark the measurements on the adult tie using a marker or pencil crayon.
Cut out the width of the re-sized toddler tie. Leave the length of the tie the same. Resew the thinner tie by sewing it inside out. Turn the tie right side out and knot it around your own neck as if you were putting it on. The knot should be proportionate in size to your toddler's shirt collar so that it correctly fits into the space between the collar ends.
Take off the tie and adjust the knot to the correct length of the tie. You should now have a large neck loop area and the smaller toddler size tie. Cut the neck loop area approximately an inch from both sides of the tie's knot.
Fold the cut areas back beneath the tie's knot and sew them in place with a needle and thread. You should now have a toddler size tie with a knot and no neck loop. Complete the clip-on tie by placing a small amount of glue onto the back of the tie's knot to attach it onto the front of the metal clip.