An interlocked pawn structure
Here is another recent interesting situation that I got involved in, in my OTB chess "career" (please don't laugh.)
Basically I am black in this game. The topic title is perhaps slightly true but also slightly misleading. Perhaps the topic title should have been: "how my opponent messed up an interlocked pawn structure!" He shall remain nameless although I suppose if anyone was so inclined they could search the ECF grading database in July!
Anyway my opponent commented after the match: "It was just one bad move by me." I replied bluntly but also truthfully: "Yes you completely messed up interlocking the pawn structure."
My opponent was only a few moves away from a dead drawn position from the opening position. Had he played f5+ and then played h3, and then moved the King over to prevent Nb4 it would have meant pointless waiting moves between the two of us.