Narrowing the veiwport will show the concept in the Note: This may cause the containing block's width to be negative. IE8 and Safari 5 shows correct rendering.
ltr test
First Box text text text text text text
ap 1
ap 2
last Box text text text text text text
rtl test
First Box text text text text text text
ap 1
ap 2
last Box text text text text text text