Step 3. A central datum, drilled into the frames, will ensure the position of the first wheelset is accurate, relative to both the CSB anchor points and the chassis' original components, such as the brakes.

The hornblock etches have a corresponding hole so that, when you've assembled the chassis, a short length of wire can be used to accurately locate the first set of hornblocks in the frames.

The remaining axles can be jigged from this axle, using axle jigs and siderods, as you would normally.