I produced the stepping board according to whether the former guard and ladder beam with four forms of connection mode, expressed as T1, T2, T3, T4. 

 From an economic point of view, the proposed width of the module as far as possible (use 125,155,185,215,245,275 Series 1, Series 2 is 125,165,205,245,275 mm, etc.) as a multiple of the length of 100mm (ie 500, 600,700,800,900,1000,1200 mm, etc.). 
 Treads tolerance: width W ± 3mm, length of the L-3mm.