Ok let's go from scratch with OB's.
- What is a thing ? -> all it can be less what it cannot
- What is an OB -> a PC
- What can't OB be as PC ? -> XB, XR, SYM, StB, StR, FTP, FBP, Lat, Hitch
- What is the common point between all those last nine PC's ? -> bar 2's H/Ls are either 1 time...