There is a one in 121 chance when zapping or engraving with an (x:0) wand of wresting another charge out of the wand, yielding the message "You wrest one last charge from the worn-out wand." and providing you with one last bit of magic after which the wand crumbles to dust. It is most commonly cited in connection with wands of wishing, where one last wish can be immensely useful; it is nevertheless possible with any wand.
A cancelled wand cannot be wrested from, as the internal charge counter is set to -1 by the act of cancellation.
Strategy
The usual technique associated with wresting is to #adjust the wand to the z inventory slot and holding down the [z] key to zap the wand repeatedly, greatly reducing the amount of real time and effort needed to extract the wrested charge. Be sure to pay attention to what's going on around you while you hold down the key, or you may end up dead without knowing what killed you.