 The rod numerals were used with the counting board. Since the counting board was any convenient flat space, it might be difficult to keep the numbers separated. So to help distinguish between the digits and adjacent spaces, there were two forms of the rod numerals. So again, the counting board is any convenient flat space, say the floor. The first form of the rod numerals, which we can call the even-place numerals, when we have to write something in ones, or hundreds, or 10,000s, looks something like this. To represent one, I'll put down a rod, a counting rod, two will be two rods, three will be three rods, and so on for four and five. For six, the way to think about six is that it's five and one. So we'll put down a bar representing five, which in this case will be horizontal, and a one. And it's helpful to think about this horizontal bar as representing five, which means that for seven, we'll put down five and two, eight will be five and three, and nine will be five and four. We can call the other form the odd-place numerals, and these are for tens, for thousands, and so on. This time our one is going to be a horizontal rod. Okay, you interns are having too much fun. Two will be two horizontal rods, and we'll do the obvious things for three, four, and five. Again, six is five and one, and in the even places, our five is a vertical bar, seven is five and two, eight is five and three, and nine is five and four. So let's put down some numbers. So we'll clear a space on the floor to set up our counting board, and it'll be helpful to mark the places. So we have our even place for ones. The next place is for tens. Those will be the odd-place numerals. The hundreds place, that's again the even forms. So 57, well that's five tens. So we represent five in the tens place using the odd forms. And if we have the marker here, we are reminded that the odd-place form start out horizontally, so we can place down five. We also want to set down seven ones, so we'll set down seven in the ones place using the even forms. And again, this rod reminds us that these forms are vertical. And it may be helpful to remember that seven is two and five. Now the clear button on our register is pretty easy. We just wipe all the rods off the board, which could also happen if you have a cat, and we go on to the next problem. We want to write 570, so 570 is 500. So we'll represent five in the hundreds place, which uses the even forms, and seven tens. So we put seven in the tens place using the odd forms. Again, it's helpful to remember that seven is five and two. Again, we'll clear the counting board. So 507, well that's five in the hundreds place using the even forms. Then seven ones, so we represent seven in the ones place also using the even forms. And it's worth pointing out that because of the different orientation of our rod numerals, it's easy to distinguish between 57, 570, and 507.