of fig8 showing the right hand member 27 the handhold bar frameworks 29 a 29 b preferably have handhold bars 31 spaced on 12 inch centers as are the rungs of the ladder 21 the side elevation view of the right hand member of fig7 and the perspective view of the right hand sleeve of fig9 show that the opposite side of the sleeve 49 from the slotted side can have a half circle cutout at the open bottom 53 this cutout accommodates the second rung 71 where the spacing between rungs may vary in so accommodating the second rung 71 the abutment of the top rung 67 against the top of the slot 55 is assured fig9 also shows a rectangular cutout opening 83 in the slot adjacent sidewall 59 this opening 83 accommodates the shoe 63 at the one end of the securing tab plate 61 fig1 in a friction fit the rung pivot lock 65 fig1 has two outwardly extending tabs a first tab 85 extending perpendicular to the plane of the lock to extend under the lock tab cover plate 77 to engage the spring plate 75 this spring plate 75 biases the lock 65 to.