wooden clapper
... that some bells are replaced by a wooden clapper for three days in a year?
... that some bells are replaced by a <b id="mwBa0"><a class="mw-redirect" href="./Crotalus_(liturgy)" id="mwBa4" rel="mw:WikiLink" title="Crotalus (liturgy)">wooden clapper</a></b> for <a href="./Paschal_Triduum" id="mwBa8" rel="mw:WikiLink" title="Paschal Triduum">three days in a year</a>?