Patent ID: 8668049

Claim:
A ladder comprising: two stiles, each of the stiles having a longitudinal connection groove on an inner side thereof; a step unit mounted between the two stiles, said step unit comprising: a hollow step having an end with a constricting opening, the hollow step having an inner cross-section profile defined by an inner tubular surface and an outer cross-section profile; a continuous inner sleeve located entirely inside the hollow step, the constricting opening preventing the inner sleeve from moving out of the hollow step, the inner sleeve having an inner thread aperture and an outside cross-section profile substantially corresponding to the inner cross-section profile of the hollow step; and an outer sleeve having an opening having a second inner cross-section profile, the second inner cross-section profile substantially corresponding to the outer cross-section profile of the hollow step, the opening receiving and surrounding the end of the hollow step, the outer sleeve engaging a respective longitudinal connection groove; and a fastener passing through one of the stiles, and the outer sleeve and being fastened to the inner thread aperture in the inner sleeve, wherein a circumference of the constricting is smaller than a circumference of the inner tubular surface.