You can choose to have boxes drawn around the pairs that are swapping (as in this example) or to draw a cross between them.
Just before a row is about to change into the next row, boxes (or crosses) are drawn to indicate the pairs of bells that will swap places with eachother. When the last bell of the old row sounds the pairs begin to swap - the digits moving smoothly to exchange places - finishing as the first bell of the new row sounds its blow.
The result is an effective animated demonstration of place notation that would enagage the interest of those new to change ringing as well as existing ringers.