Lay the sweater out on a flat surface. Insert the sheet of cardboard between the front and back of the sweater and brush out any wrinkles with your hand.
Place a 5mm crystal along the shoulder of the sweater, and use the hotfix tool to adhere it in place, following the tool instructions. Be sure to leave the tool on the crystal for about 25 seconds.
Continue to adhere one 5mm crystal at a time in a straight line across shoulder of sweater, using the hotfix tool.
Repeat this process to make a second row of 5mm crystals next to the first line, shorter than line 1.
Repeat Steps 1 and 2, alternating lengths of lines and crystal sizes, until shoulder is covered in a sunburst pattern (as shown), or to your desire.
When your design is complete and the sweater has cooled, check crystals for security. Re-heat, using tool if necessary.