There are hundreds of threads about toilet cisterns, traps, suite types, but this thread is the nearest that come to the problem that I am raising. This is about the shape of the pan, bowl or commode; specifically the vertical profile of inside of back and front. This is about toilet pan which is not self-cleansing. I have been lucky not having to use one of this type of pans where I lived through most of my life. I have seen one of my relatives had installed one, and I have just been in a hotel in Italy that has one of these horrible toilet pans. The en-suite even had a bidet. If the faeces land on a sloping wall of various gradient from almost flat to up to 45 or 60 or even more degrees, the faeces will stick to the pan and you might have to flush 10 times to get the pan cleaned, unless you brush and clean it yourself. If the back of the bowl is nearly vertical and front wall is sloping where the urine might flow down, that is the normal pan that functions well with least problem of cleansing. If that profile is reversed for some awkward reason then it is a dirty toilet. Once I used one of these nasty almost flat bottom pans in a ship used as a hotel; fortunately it had a miracle flushing syphon-cistern that cleaned itself without a problem. I am bit unhappy about the existence of this abnormal shape of toilet pan which is not self-cleansing, because I might run into one of them now and then.