Bob Garrison wrote:

Catch them in the act and squirt them with water. You won't need to do it
very many times before they get the message.

This can work, but you incur in the risk they learning that they must be
carefull to not be caught. If they get water *only* when you are near,
then they learn to do that things when you aren't...

Is there any way to make the pieces have a really bad taste? I think
this could work. This, or putting a box over the board, protecting it...

[]s
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Cesar A. K. Grossmann