Place value slides are a fantastic resource to teach what happens when numbers are multiplied or divided by a power of 10 (10, 100, 1000 or 0.1, 0.01, 0.001, etc.). The "traditional" method of teaching students to "move the decimal point" is crap, and should NEVER be taught. But to listen to lots of young adults (such as many of my preservice teacher students), that is exactly what they have been told. And unless they understand what I teach in this video, that's what their students will learn.
Decimal points do not move. Ever. Even in a bad math lesson. The decimal point exists to separate ones from tenths, or whole number places from decimal fraction places. Telling students to move the decimal point is like asking them to rearrange the letters of the alphabet because it happens to suit the teacher's strange ideas of alphabetical order.
Use a place value slide to demonstrate the "shifting" of every digit left or right as a number is multiplied or divided by a power of ten. Making a place value slide involves use of a sharp knife, and so should be done by an adult. But the effort is worth it in demonstrating clearly what happens within the base ten system when multiplying by a power of ten, such as when converting metric measurements or calculating with percentages.
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