... . The half switched diamond provides no checking for the "K" crossing. Jim. posted: 12 Apr 2015 13:38 from: Ian Allen Jim, The check rail for the other K crossing is there. Ian posted: 12 Apr 2015 14:40 from: Martin Wynne Ian Allen wrote: The check rail for the other K crossing is there. Hi Ian, Jim is right, check rails control the crossings in the opposite rail. You don't have any check rail for the fixed K-crossing: 2_120929_320000000.png Because there is no check rail at A, a wheel-set moving left to right at B can move sideways, such that the opposite wheel flange may hit the nose of the point rail at C, or even go the wrong side of it. The open switch blade at B can't provide any checking because the switch opening is always significantly greater than the check rail gap -- if wheels hit an open switch bade it can damage the stretcher bars and detection gear. So this is definitely not a prototypical arrangement ...