Pegs. I have to use the same coloured peg on each line of the washing line. Each of the lines can be different from each other, but every peg on a single line must match. I've always been like it and if anything am getting worse. Once in a blue moon when my DH actually helps hang washing on the line he thinks its hilarious to deliberately use different coloured pegs. All that happens then is that I have to go along and re-peg everything.

I also have to have all the handles of my coffee cups going in the same direction at the same angle.

All the towels need to be hung exactly evenly over the rails.