Sentence:  On those occasions when <WSD>lunettes</WSD>, "custodia" and monstrances are used, the sacristan needs to be sure that the lunette fits into the given monstrance, that the host fits into the lunette, and that the host is put out before Mass for consecration. 
Meaning of the word marked with <WSD> tags:  A '''luna''': a crescent-shaped receptacle, often glass, for holding the (consecrated) host (the bread of communion) upright when exposed in the monstrance. (from 19th c.)