Final answer:
The effective closure of a church's back door depends on the church's architectural design and era. Medieval churches like the one with Bernward's bronze doors had complex mechanisms suited for heavy doors. Later architectural innovations like flying buttresses also impacted church design but were more about wall support and window size than door mechanisms.
Step-by-step explanation:
The most effective way of closing the back door of the church likely depends on the architectural design and historical context of the church's construction.
In the case of the massive bronze doors of the church at Hildesheim, created by Bernward in single pieces, the significant effort exemplified in these doors reveals the complexity involved in their operation.
These doors, being large and heavy, likely required a mechanism or a technique suitable for their grand scale, though specific historical details of their closing mechanism may be lost to time.
The use of thick outer walls in church construction during the medieval period was meant to support the structure, especially when large windows were not commonplace due to the threat of structural failure.
Mention of flying buttresses comes into play as an architectural solution allowing for larger windows and more light in later churches, but again, their relation to door mechanisms is more tangential, relating to the overall structural ingenuity.