Lots of young children can count to 10. They recite the numbers with some rhythm always starting at 1 and ending at 10. But they don't actually know the quantity assigned to the number. That's where the Number Rods come into play.
The Montessori Number Rods are ten wooden rods in graded length, one decimeter (just under 4 inches) to one meter. They are colored red and blue in alternate decimeters. The number of segments in each rod represent the number of that rod. It's a nice material to teach 1-10 because children learn the quantities of numbers, the names of numbers, that each number is a separate entity and how to count one-to-one correspondence on a fixed set of materials.
Now, if you don't have the actual material -- you could easily and inexpensively make something like them. This tutorial was completed for under $10! I've also seen people use red and blue legos. But once you have them -- here's what to do with them:
Start by bringing all the Numbers Rods to the floor, on a small rug preferably. Place the rods randomly with the left edges of the rods (they should all be red) aligned with the left edge of the rug. Then, silently, build a striped stair ensuring that all the blue ends are to the right. The child may immediately want to join in building the stair. If so, that's great!
You should sit with the Number Rods in front of you and the 1 rod should be on the left. The child should be next to you. Pull down the first three rods and give a 3-period lesson on rods 1, 2, and 3. What is a 3-period lesson, you ask?
First Period: Touch the 1 rod and say "One. This is one". Then move up to the 2 rod and start counting left to right. When you touch the red segment you say "One" and move your hand to the blue segment and say "Two. This is two." Then move up to the 3 rod and start counting left to right. When you touch the red segment you say "One" and move your hand to the blue segment and say "Two" and move your hand to the red segment and say "Three. This is three." If you are with a very young child, say 3 or younger you can repeat yourself once more and say "One. Two. Three" while touching that corresponding rod.
Second Period: Next ask the child to show you a certain thing. For very young children, you may want the first thing you ask them for to be the last thing you just showed them. For instance, with rods 1, 2, and 3 if you just said the word "Three" while touching the 3 rod your first instruction should be "Show me 3." Then "Show me 2." Then "Show me 1." Ideally the child will be able to show you what you asked without hesitation.
Third Period: Lastly, you want to ask the child to recall what the name of the rod is without you giving them a verbal cue. So pointing to the 1 rod and asking "What's this?" will encourage the child to recall the number "One" from memory. Do this for rods 1, 2, and 3.
Rather saying saying "good job" or "nice!" instead give a smile and say with excitement "you know rods 1, 2, and 3". Depending on the interest of the child, you could continue with a 3-period lesson for rods 4, 5, and 6. And then going even further, depending on the child's interest, you could show rods 7, 8, 9, and 10. Some children like to do this all in one day, others like to stop and wait for a different time. Either way is fine. The points of emphasis include counting the rods precisely, teaching the quantities, for children to realize that numbers have names and that the 10 rod is much longer than the 1 rod. Whether you have the Number Rods or you make your own material the control of error should be that if the child places them out of order, the rods will not be aligned and there will be visual disharmony.
Once the child is comfortable with the Number Rods 1-10 you can play games with this material, too. Keeping the rods on a rug on one side of the room, you could ask the child to wait on the other side of the room. Bring one rod to them (any rod) and ask them to bring you the rod that is "one larger". This means if you brought them the 6 rod -- they should bring you the 7 rod. You can ask them to get "one shorter" or "two larger" or "two shorter". Be sure they are confident with the numbers before you try these extensions as we always want to strive for success.