This video from oorail.com introduces the basics of elevating OO/HO scale model railway track using Hornby R909 Elevated Track supports. The R909 pack includes 18 track support piers for incrementing sizes, there are a total of 9 different sizes and two of each size. This allows you to elevate the track and bring it back down to the original height. The R909 supports have a minimum spacing of 1 support per 24 sleepers and support a maximum height of 80mm.