The correct German phrase for that would have been "auf den Turen".
In the big picture whether Luther nailed his theses to the doors or adjacent to the doors is of little consequence. Most churches had and have bulletin boards, The church at Wittenberg was no different.
I am saying that there is no evidence at all to claim that the theses were nailed anywhere. Let alone on a church door, or multiple church doors or adjacent to multiple church doors.
Most churches had and have bulletin boards, The church at Wittenberg was no different.
The bulletin-board is a comparatively recent phenomenon. It is first attested in the early 1800s. Pasted handbills are older. Scattered leaflets are older than that, and were actually known at the time.
And, of course, the 95 theses were composed in Latin.
Printing was in its infancy at the time, and literacy was relatively rare. Literacy in scholastic Latin was arguably even rarer.
The tiny University of Wittenberg was not even 15 years old when Luther wrote his theses - it was not Paris where hundreds of passersby could be expected to be able to read and discuss theological papers written in Latin. 99% of the people in Wittenberg could not read the language the theses were written in.
Fewer could follow the arguments being made in them.
In context, it would have been an absolute waste of time to do this.
The reason why I bring up the legend of The Nailing of the 95 Theses, is because it is an example of the way folklore tends to dramatize and distort history.