The answer
a. A wooden box on top of the altar, in the middle, is called in Coptic Πⲓⲧⲟⲧⲥ (pi-tots)
which means “throne,” and is used to preserve the chalice (during the Liturgy). Usually it is cubical in shape, and the top is covered by two flaps.
b. It is called a throne because it represents the presence of the Crucified Lord.
c. It is also an ark because it looks like the ark of Noah in which Noah and his family
were saved. Similarly, through the blood of the new covenant in the chalice which is kept in this ‘ark’ we are saved.
d. Its name also corresponds to the Ark of Covenant in the Old Testament since the latter
contained the following: the two tablets of the Law, Aaron's rod, and the golden pot of the manna, which as a symbol of the true manna, the life-giving Body and Blood of Christ (John 6).
Fr. Tadros Yacoub Malaty