In these Sudoku variants there are "holes" in the diagram.
Staircase Sudoku:
https://www.janko.at/Raetsel/Sudoku-Varianten/024.a.htm
Ten Box Sudoku:
https://www.janko.at/Raetsel/Sudoku-Varianten/027.a.htm
(It seems that I do not have the right to add a poll to a posting. detuned, please!)