This week I was trying to help my students understand rounding to the nearest ten. I noticed they kept looking up to the number line I have on the wall. Then I got the idea to give each pair of students a meter stick at their desk. It really worked well. One would find the number and the other would see which ten was closest. On the meter stick the numbers 10, 20, 30, etc. are larger and darker. We even used it for rounding to the nearest hundred by adding a zero to each number. The only trick is the need for lots of meter sticks.