Reshaping a rectangle to swap its length and breadth
Transforming the oblong o t u x into rectangle a b c d via a square (prop. 10)
This page carries a numbered proposition (10) on the "inversion of the measures of a rectangle." Leonardo shortens the long rectangle o t u x until it swaps its breadth for its length, turning it into the rectangle a b c d by first reducing it to the square a m o n (by his fifth proposition) and then rebuilding it (by his sixth). A semicircle enclosing an inscribed square and rectangle is drawn at the upper right; faint additional writing, partly show-through from the facing leaf, appears lower on the sheet and is not part of the transcription.
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Swapping the breadth and length of rectangle o t u x
The oblong o t u x is to be lowered until its breadth becomes its length, producing the rectangle a b c d of height S o. Leonardo reduces o t u x to the square a m o n by his fifth proposition, then reconstructs the rectangle a c b d from that square by his sixth. This is presented as the converse of the preceding construction.