A ladder comprising: a first stringer and a second stringer spaced transverse from each other, with each of said first and second stringers (22, 24) defining a channel; a plurality of crosspieces disposed in said channels of said first and second stringers for rigidity; a plurality of rungs spaced along and coupled between said first and second stringers (22, 24), each of said rungs including: a horizontal portion extending from said first stringer to said second stringer, said horizontal portion having a top surface and a bottom surface spaced from and opposite said top surface; and a vertical portion extending generally perpendicularly away from said bottom surface of said horizontal portion and extending from said first stringer to said second stringer, said vertical portion having a front surface and a rear surface spaced from and opposite said front surface; and a plurality of ribs spaced along and coupled between said horizontal and vertical portions (40, 42) of said rungs wherein said ribs extend from said bottom surface of said horizontal portion to at least one of said front and rear surfaces (48, 50) of said vertical portion; said first and second stringers (22, 24), said crosspieces, said rungs and said ribs being integrally formed together as a single monolithic unit characterized in that said rungs are coupled between said first and second stringers (22, 24) opposite fro said the open side of channels defined by said first and second stringers (22, 24). a first stringer and a second stringer spaced transverse from each other, with each of said first and second stringers (22, 24) defining a channel; a plurality of crosspieces disposed in said channels of said first and second stringers for rigidity; a plurality of rungs spaced along and coupled between said first and second stringers (22, 24), each of said rungs including: a horizontal portion extending from said first stringer to said second stringer, said horizontal portion having a top surface and a bottom surface spaced from and opposite said top surface; and a vertical portion extending generally perpendicularly away from said bottom surface of said horizontal portion and extending from said first stringer to said second stringer, said vertical portion having a front surface and a rear surface spaced from and opposite said front surface; and a plurality of ribs spaced along and coupled between said horizontal and vertical portions (40, 42) of said rungs wherein said ribs extend from said bottom surface of said horizontal portion to at least one of said front and rear surfaces (48, 50) of said vertical portion; said first and second stringers (22, 24), said crosspieces, said rungs and said ribs being integrally formed together as a single monolithic unit characterized in that said rungs are coupled between said first and second stringers (22, 24) opposite fro said the open side of channels defined by said first and second stringers (22, 24). a horizontal portion extending from said first stringer to said second stringer, said horizontal portion having a top surface and a bottom surface spaced from and opposite said top surface; and a vertical portion extending generally perpendicularly away from said bottom surface of said horizontal portion and extending from said first stringer to said second stringer, said vertical portion having a front surface and a rear surface spaced from and opposite said front surface; and a plurality of ribs spaced along and coupled between said horizontal and vertical portions (40, 42) of said rungs wherein said ribs extend from said bottom surface of said horizontal portion to at least one of said front and rear surfaces (48, 50) of said vertical portion; said first and second stringers (22, 24), said crosspieces, said rungs and said ribs being integrally formed together as a single monolithic unit characterized in that said rungs are coupled between said first and second stringers (22, 24) opposite fro said the open side of channels defined by said first and second stringers (22, 24).