Where it clips in
The 1SAM101904R0001: Aux blocks in this ABB family mount to the front face of the matching MS manual motor starter, latching on without taking an extra DIN-rail slot. That keeps the panel footprint unchanged when adding a status feedback path — the same DIN-rail pitch that the starter occupies is what the assembled pair occupies. Wire the side-car through a spring-cage or screw terminal on the block face, then land the run back to the control wiring duct; the block's terminals are on the front, so the wireman can land them after the main power terminations are torqued.