Specification:

Series L1B & L1D Ladder

The  series L1B and L1D ladders as manufactured by Halliday Products Inc. of Orlando, Florida, shall be constructed 
entirely of aluminum. The rails shall be 1/2" x 2 3/4" (13mm x 70mm) aluminum extrusion and shall be spaced  16" (406mm) 
apart. The wall mounted standoffs shall be 3/8" x 2 1/2"3/8î x 2 1/2î (10mm x 64mm) flat bar and welded to the rails at 
a maximum of 60" (1.5m) on center. The standoffs shall be a minimum of 7" (178mm) and manufactured to fit flush with the 
wall. 1 3/8" (35mm) diameter type "D"  rungs with flat resistant surface shall be spaced at 12" (305mm) on center and  
welded to the outside of each rail.