1. Draw a square, for example 10x10 mm.
Tip 1: Hold Ctrl while using the Rectangle tool (Toolbox > Rectangle tool or F6), to create a square.
2. Duplicate the width of the square.
Tip 2: If you hold Ctrl and drag the center right handle, the size will duplicate (or triplicate, etc. as it enlarges in increments of 100%).
3. Make a duplicate of the rectangle, with a small distance between each.