... . A sample of C&L rail could be useful. Maybe several short lengths (an inch is plenty) from different batches. The nominal dimensions of the jaw apertures are (foot width/web thickness) in mm A 0.8, 0.3 B 0.8, 0.4 C 0.8, 0.5 D 0.9, 0.3 E 0.9, 0.4 F 0.9, 0.5 I had to guess the foot height. They are are all the same at 0.4 mm. Here's what they should look like side on. A is on the left. 2983_081409_380000000.gif From here A, B and perhaps C seem to be a good fit on SMP rail. B is probably best. The material will actually flex a bit but if you go too far it snaps. Cheers! Andy posted: 8 Jul 2018 19:27 from: Martin Wynne Andrew Barrowman wrote: I do not know to what extent any of them, other than STL, would help. I can post examples if you think any of them would be better. I'm not too optimistic but it's worth a shot ...