... remember being shown the pattern shop at Taylor Brothers' Sandiacre works where they had wooden patterns for every rail section they had ever had to use. They were able to adjust the spacing of the jaws for a double chair to suit Thanks Judi. Are you saying that whenever a crossing was laid curviform, special chair castings would be provided? Even say when the gang are laying out sidings in a goods yard from second-hand material? I have tweaked the maths a little to make the spacings a bit less discontinuous: 2_300755_320000000.png A 1:8 crossing normally has just two crossing chairs beyond the "B" chair, on the "C" and "D" timbers, bridge chairs being used on one or both sides beyond there. A standard L1 bridge chair requires 7" clear from the rail running edge on the key side, so allowing for an angle between them we can see where the 15" separation limit comes from, below which the special crossing chairs are needed. (L1 chairs can get quite a bit closer if you ...