Such a simple thing we have all grown to recognise and take for granted . Would the keyhole slot work better the other way up ? The slot was changed to a kidney shape by Stanley to prevent the lever cap creeping backwards . There no forces in play to push the lever cap forwards . There is plenty of room to release the cap either way . The bulge in the cap iron (screwed to the blade ) can produce a backward pressure on the lever cap if the bulge is ahead of the front edge of the lever cap .
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