this came up before and I, wrongly maybe, have used the TOP section... to no ill effects (motors run ok) I always felt that (looking ) \TOP/ created the widest gap position recommended which I would then set at 20
the tool itself shows that the KEY does not line up with the tool's pointy arrow and is offset by maybe... 15 degrees indicating it does not use the key itself as the high point for the rubbing block.
is this why the gap itself needs to...just begin to open when the tool is used
,,,that being the firing point on the plugs....leaving the point gap to continue "widening as it reaches the TOP marking ????
btw I am now using the tool