... a horizontal section, which was confusing me in the previous photo. Even the flattest masonry arch doesn't have a horizontal section in the middle. Many thanks to Fraser for such a detailed explanation of arches. cheers, Martin. Hello Martin I've now stuck a new piece of card in place, properly and trimmed to size properly! And here it is sitting on the edge of the layout where the light is better. Tell me what you think, does it throw light on my lack of clarity previously? Kind regards Andrew 2787_291821_150000000.jpg posted: 29 Apr 2020 23:55 from: Andrew Duncan FraserSmith wrote: Just to add to the arches debate, many, many "elliptical arches" aren't elliptical but three or rarely five centered. They have a large radius to the centre section that joins to smaller radius section(s) towards the springings. Much easier to make the centring for and only two (or three) different shapes of voussoirs rather than every course being different to each other as the effective radius changed from small to large. Martin's ...