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Based on observation around the NSWGR the '6 bolt' fishplates only seem to have 4 bolts used. The fishplates are used to connect lengths of rail and the rail joints are staggered. The 6 bolt fishplates are used on main lines, passing sidings and possibly major sidings in yards. The 4 bolt fishplates are used in sidings and possibly pioneer branch lines.
The 3D printed model fishplates when glued to the side of the web of HO Code 70 or 75 rail do not interfere with NMRA RP25/110 and RP25/88 wheel flanges.
Fishplates are also available without the bolts.
The image of the 3D printed model fishplates show them opposite each other but this was done as a test to ensure that NMRA RP25/110 and RP25/88 wheel flanges would not hit the fishplates (which they don't).