The Texas Essential Knowledge and Skills (aka TEKS) for Kindergarten require that all children be "fluent" up to the number 20. That means addition, subtraction, identifying and writing the numbers, and making groups up to 20.
This is an activity that helps them count to 20 by 5s, reinforces fine motor skills, and is just plain fun to do.
Take a sheet of construction paper and have them fold it in fourths. They then cut out pictures of objects from a magazine and glue 5 in each square. Thus 5 x 4 = 20.