How do you build a square from this figure? 
If you can use only this figure, what is the LEAST number of such figures that you can use to build a square ?
You can use any isometry to build a square and it must be full from the inside.

One can also generalize this; if you kept going with the spiral pattern (placing a strip of 7 squares at the end of the previous strip) for all 4 pieces, you would have a square of 8 units.
It's not hard to show inductively that you could continue this without bound to make arbitrarily large squares with even side length.
