This year, and last year I used black leather cord, which in terms of durability lasts forever. My son kept his on for ages, last year I used colourful beads but this year we went for a classic gold and black format.
Although the knot involved looks complicated at first you will get the hang on it very quickly. I will give the sizing for an adults rakhri but for a childs one I would reduce the measurements by 5-10cm depending on the size of their wrists.
1mm Leather Cord
Ruler/ Tape Measure
1. Cut one 40cm piece of cord and one 60cm piece of cord
2. Sellotape the 40 cm piece down
5. To make this explanation easier I will label the strings 1,2 and 3 going from Left to Right
6. Take S1(string 1) and place this over S2(string 2) and under S3(string 3)
10. Take S1 under S2 and up through the loop made by S3
11. Pull together and keep on repeating on alternative sides until you have formed 10 knots
14. Knot the cord for one final secure hold and cut off any remaining cord
15. You can slide the knots down to ensure the are in the center and that is it, one rakhi made