A number expander is a great way to show children how regrouping works i.e. 45 tens is 450 (45 tens and 0 ones) or 4 hundreds 5 tens and 0 ones. These files are made student size (not teacher demo).We printed them on normal paper and then used packaging sticky tape (the wide stuff) to "laminate" them as using real laminate is too thick to make the folding easy. Pre-fold the valleys and mountains before covering with sticky tape. To really flatten place under heavy book over night.
Use whiteboard markers to draw numbers (we originally thought we would make numbers but that was too fiddly).
Check out this one minute video for an explanation.
We use Linear Algebra Blocks to teach decimals; the pictures of pipe and washers are LAB, delete if not needed. An easy way to mimic this is to give students straws: one whole, one cut into tenths to give a sense of size. http://www.mathsheroes.com.au/2015/01/lab-linear-algebra-blocks/