This portable stapler was purchased for a job that ran over 5,500 staples. While not perfect, it saved my hand from hand staplers. Of the 5,500 staples, about 500 staples/staples probably failed. I think the stapling failed mainly because the shackle hole got too big or out of spec. In theory, the hole should only be big enough for a staple to fly out, but it should be small enough for the staple blade to hit the staple squarely and knock the staple out in a perfectly straight path. The opening