Grow math skills with birds on a fence! Introduce, practice, and reinforce numbers with this engaging On the Fence Number Line -20 to 120. Introduce ten numbers at a time, display as a full line, or stack as a number chart. Use the birdhouses to demonstrate the concept of odd and even numbers. Colorful birds help with hands-on activities such as skip counting. There are endless ways to display the number strips to support lessons and make learning FUN.