The word corporal comes from the Latin word corpus, meaning body. It is the cloth on which the paten and chalice are placed during the Holy Sacrifice of the Mass for the consecration of the most holy Body, Blood, Soul and Divinity of Our Lord. The purpose of the corporal is to catch any fragments of the consecrated host that may fall away from the sacred host. Folding it improperly, flipping it over or shaking it out cause the fragments to be thrown to the floor. The corporal is a square linen cloth. It is usually about 18 to 19″ square. The corporal should not be left on the altar, since that would defeat its purpose.
Why is it that many priests/ deacons no longer know how to open and refold a corporal? I have seen priests and deacons, pick up, shake out and flip over the corporal, showing they do not know why we use one. Here is a quote from “The Ceremonies of the Roman Rite Described” by Dom @Alcuin Reid (Pg. 66 & 85). Even if a priest does not celebrate the Extraordinary Form, he can learn a lot from our tradition.
“Then he spreads the corporal, placing the unfolded corporal in the middle of the altar and opening out its sides, and then the top and the bottom, ensuring that the creates face upward (so that any fragments are contained within it when it is folded again); the front edge should be about an inch from the front of the altar.”
And on refolding it:
“He folds the corporal beginning with the fold nearest himself and puts it back into the burse.”