(extract from teachers guide)
The letter Tzadik is one of the only letters to have a "pouch" to store charity coins in. The hebrew word for Charity is Tzedokah, which begins with the letter Tzadik.
When students see the "pouch" it triggers their memory of the Tzedokah story, that will lead them to recall the name of the letter, as Tzedokah begins with the letter Tzadik.
Other imbeded hints in the lesson plans include methods to ensure students don't mix up 2 similar looking letters.
For example, To avoid students mixing up Tzadik with letter Ayin, they will see how Ayins pouch is too low/deep to reach for coins.
View Tzadiks worksheet (extract from the workbook). Notice how all activities in the workbook follow the theme of the letter that reinforces what was learnt. It's a truly remarkable workbook.