... butts against the projection. The seat (and hence the DXF block reference) is longer under the wider L1 bridge chairs: 2_212217_190000000.png That's as far as I've got. The next job is to try building the jaws, and fitting the keys. I will post you a DXF file shortly so that you can test replacing the block markers with your own chairs. cheers, Martin. posted: 22 Jul 2018 05:54 from: Martin Wynne Hi Andy, Here is a DXF file for you to experiment on. 2_220019_450000001.png 2_220019_460000002.png A bog-standard Left-Hand B-6, and a RH A-4.5 with negative curving and equalized timbering. EM gauge. So far there are only 4 blocks defined in the file: S1L and S1R are identical mirror-image blocks, for ordinary REA S1 chairs. L and R versions allow the replacement blocks to have keys driven in opposite directions: 2_220019_450000000.png L1L and L1R are ditto for L1 bridge chairs. These are longer blocks, to match the wider L1 chairs. The switch chairs are temporarily ...