Take an unrooted ten-leaf tree:

The backbone tree has 10 leaves; 17 test trees were generated by adding an clade of three leaves at each of the 17 edges of the unrooted backbone tree.

These are trees T_{1}–T_{17}.

For each of these trees – we’ll consider T_{1} first – we can then move the eleventh leaf to each of the other edges of the tree, giving trees U_{1.1}-U_{1.19}:

or the cherry containing the twelfth and thirteenth, giving trees V_{1.1} to V_{1.19}:

Two trees occur in both U_{i} and V_{i}, i.e. they can be generated by moving one leaf or moving two leaves. These trees are excluded from further analysis.

We then expect the distance from T_{i} to U_{i.j} (i.e. move one tip to a new location) to be less than the distance from T_{i} to V_{i.j} (i.e. move two tips to the same location)