at a preselected location relative to the pivot means 18 in the preferred embodiment the stop 28 is an edge portion of the frame 12 that is formed by an opening 30 extending through the frame 12 in the installed position the step member 16 extends from beneath the frame 12 through the opening 30 and to pivot means 18 referring to fig2 the preferred stop 28 extends from a first end 32 immediately adjacent the stop 28 along the frame 12 to a second end 34 of the opening 30 the second end 34 of the opening 30 preferably is greater than the first end 32 as measured transverse the elongated frame 12 by this construction angular impact against the step does not damage the step 16 for the increasing width of the opening 30 permits limited lateral movement of the step member 16 further the angular sides 36 38 of the opening 30 function to guide the step 16 to the first end 32 during movement of the step from the second end 34 toward the first end 32 the sleeve 22 can also have a width sufficient for permitting limited movement of the sleeve 22 along pin 24 lateral movement can also be provided by mounting the step 16 to the frame 12 via a bearing the step member 16 has a step portion 40 for receiving the foot of an operator the step member 16 is pivotally movable and of.