Danger, Danger !!
There is not as many pop rivets in a 9 as in a 12, but still we use them in various places. After finishing a job, I make sure I end up with one stem for every pulled rived and then toss them in the bin.
Imagine one of those stems left in the fuselage somewhere, gets forgotten about and later on starts corroding away in an unaccessable area, or moves about and blocks your controls, or bridges a couple of wires (spark-spark-smoke), or gets thrown around under the cowl, or...........(fill in whatever nasty things you can think of, by yourselves, here)..........
And don't forget the extra weight either!
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Also I make sure they are not left on the garage floor, because they make a perfect tire puncher! I Would hate to have to drive out, to help the wife change a tire, some day, finding a pop-rivet stem in there!
(yeah, yeah, I know, those days my car is outside anyway
)
Take care, Tonny.