An SS stair ladder is an angled access structure comprising two parallel inclined stringers (side rails) supporting a series of horizontal treads at equal rise intervals — providing a safer, more comfortable ascent than a vertical ladder for routine daily access, while occupying less floor area than a full-width staircase. Standard stair ladders operate at 45–60° inclination with tread depths of 150–250 mm and risers of 200–250 mm. Alternating tread stairs (ship ladders) operate at 60–75° with left-right alternating tread cutouts — requiring ascending operators to step left-right alternately, enabling the same structural stringer spacing as a standard stair ladder but at a significantly steeper angle in a much smaller floor footprint.

Stringers are cut from SS flat bar (80×10 to 150×12 mm) or channel at the required angle. Treads are fabricated from chequer plate, bar grating, or perforated plate to match the connected platform flooring type — tread width typically 600–900 mm clear. For stair ladders, full-depth symmetric treads (150–250 mm front-to-back) are welded to the stringers at equal centres. For alternating tread stairs, each tread is cut to alternate left and right, leaving a 75–100 mm full-width strip at the back of each tread for the foot placement — right tread has full depth on the right half and cutaway on the left, and vice versa. Handrails (Ø40 or Ø48 CHS, 900–1,100 mm vertical height above nosing) run continuously along both stringers from landing to landing.