What are the different types of obstacle in National Hunt racing?

What are the different types of obstacle in National Hunt racing?  With the exception of the confusingly-named ‘National Hunt Flat Race’, which involves no obstacles at all, all National races are contested over hurdles or fences. Hurdles are the lower, less substantial type of obstacle. Each hurdle consists of brushwood, cut and fashioned into panel that stands at least 3’6″ high. Individual hurdles, which must be uniform across the racecourse, are installed, side-by-side, to create what is known as a ‘flight’ of hurdles. Each flight, of which there must be eight in the first two miles of a race, measures a minimum of 3’1″ high and 30′ wide.

By contrast, steeplechase fences are higher and more substantial; they consist of a rigid frame, made of steel or wood and stuffed with real birch cuttings or plastic birch, to create an obstacle at least 4’6″ high. Unlike hurdles, which are often knocked flat during a race, fences are much less forgiving . Furthermore, a so-called ‘plain’ fence may be preceded by a shallow ditch, a few feet wide, to create an ‘open ditch’. The cross country course at Cheltenham, which is only used a few times a year, features idiosyncratic obstacles, natural and man-made, including living trees, shrubs and bushes, banks, ditches and rails. It is very much a ‘specialist’ course and the only one of its kind in Britain.