The tool opens with an empty screen onto which you can drag Base 10 blocks from the dock on the left. The dock contains:

• Single cubes (to represent ones)
• Rods of 10 cubes (to represent tens)
• Flats of 100 cubes, as a 10x10 sheet (represents hundreds)
• Blocks of 10x10x10 cubes (represents thousands)

Clicking the ‘Show total’ button reveals the total number of units currently on screen (click again to hide this information).

Clicking Reset undoes all changes you have made, returning the tool to its default state.