# CDSL Bridge: Simple Shaft

- Use for a single cylindrical rod, pin, spacer, or stepped shaft, not an assembly.
- Invariants: one main axis, one coherent solid, axial segment lengths/diameters, and secondary features referenced to the axis.
- Use a circle plus `extrude_add_blind` for a uniform rod; use a closed side profile plus `revolve_add` for steps, shoulders, tapers, or grooves.
- Add end holes, flats, slots, or keyway-like cuts only after the primary body. Finish last.
- Do not invent bearings, gears, couplings, or real thread geometry when not requested.