Openings in shafts, galleries with an incline of more than 45°, and openings such as those provided for the passage of lifts, or such as chimney shafts or trap doors, which may exist in the floors of a building as well as in the floors of scaffolding, gangways or any other installations, must be enclosed or closed off :
1° Either by a guardrail placed at a height of 90 cm and a plinth at least 15 cm high;
2° Or by a temporary jointed floor suitably fixed;
3° Or by any other equivalent device.