This is the first block, with a big left margin. At the end of this block is a left float which should be square. Text that follows this box should flow to the right of the float or go below it; no text should be on the left of the float.
This is the square left float.
This is the second block. It is sized so as to be just narrow enough to fit in the gap to the left of the float. Text should not want to be to the left of the float, since it is a left float in flow, so instead all the text should just move below the float.