Monstrance, also called ostensorium, in the Roman Catholic Church and in some other churches, a vessel in which the consecrated Eucharistic host (the sacramental bread) is carried during processions and is displayed during certain devotional ceremonies. Both names, monstrance and ostensorium, are derived from Latin words (monstrare and ostendere) which mean"to show". First used in France and Germany in the 14th century, when popular devotion to the Blessed Sacrament grew, monstrances were modeled on pyxes or reliquaries, sacred vessels used to carry the host or relics. The host was represented in a glass cylinder mounted on a base and surmounted by a kind of metallic crown. In the 16th century, the monstrance took on its current form:a circular window set in a cross or surrounded by metal rays. The host is placed in a support called a bezel, which fits into an opening behind the glass.
Monstrances are commonly used during Eucharistic adoration, during which the faithful come to pray for the real presence of Jesus in the Eucharist. Some churches offer perpetual adoration, where a monstrance with the host is always available for prayer and contemplation, often in a dedicated chapel. During a special service called"benediction", a priest uses the host in a monstrance to bless the faithful; this is considered a blessing from Christ.