Been tiling for donkeys years. Pretty good at it! Until. Tiling a big room a little while ago. Finished one part of the room and to continue I had to put a level line across a doorway. Simple enough, done it before. Put the bottom of my level on top of the tiles on one side of door, got level level, and put a pencil line on, wait for it, the top of the level on the other side! Started tiling. 12 metres later. F##k. Amaturish or what.