The original plastic key for my boat's kill switch broke a few weeks ago. A few iterations with my printer and I had a replacement.

My first attempts had problems with too large of a bridge, so I added some slanted sides to the design. I still had a little droop, but it fits the kill switch with just the right snugness so I called it a day.

It took me 8 iterations before I had a working copy. First iteration illustrated the problem with too big of a bridge (solved with slanted sides). Next seven iterations were necessary as Sketchup output some intersections and faces that slic3r didn't like. I finally figured out the faces on iteration 8.

Printed in red ABS to match my boat. Photo shows the leash and original sunbleached broken part.