Guy decides to use his router to plow some grooves in plywood instead
of putting the dado blade on the TS. He needed the groove to be a hair
over 3/4" so he put in a 5/8 bit and set the fence for the first pass.
Cut all of the pieces without trouble with this setup. Then he
adjusted the fence for the second pass and nibbled a little of the end
of the test piece and checked the fit. Just where he wanted it, now to
make the final cut (know where this is going yet?).

He starts feeding the piece through and about halfway thru the cut the
piece flies off the router table!
He picks up the piece and examines it, must have been that knot that
flung it out. Good thing it was the test piece. Starts on the next
one and halfway through the piece flies off the table. WTF!

Shuts everything down. Look at the router table wondering which is
left and right, start thinking back to the craftsman table he used to
have...which way did that arrow point? No. I'm going the right way,
it must be the x-grain of the plywood causing the problem. Lets try
this again...

Doesn't fly off the table this time, but almost. Newbie examines the
bit expecting to find a bent cutter or some other explanation other
than user error, nope. Then he looks at mangled piece expecting the
wood to say 'sorry won't happen again', no response. Grasping wildly
the newbie decides that the router must be spinning backwards... time
for a break.

A few minutes sitting on the chair trying to figure out how the
polarity was reversed in his router helped the newbie realized he was
trying to cut on the back side of the bit.