this has probably been mentioned before. it may be possible to find new techniques by swapping the words box for row and vice versa (or box for column).
For example a well known technique: if a candidate occurs in only one row in a given box then that candidate cannot occur in that row in another box.
Swapping box for row in this gives: if a candidate occurs in only one box in a given row then that candidate cannot occur in that box in another row.
This second technique is a generalisation of generalised x wings.
