My first two Mistresses used face slapping to punish me and to put me in my place.
They employed a hand signal to me that told me to kneel in front of them so they could more easily slap my face. This would occur at any time i displeased them.
FOr me, it made me feel like a lowly piece of nothing when it was done, especially if done in the presence of others, as was done many times.

slavedoggieboy