Is there some sort of trick to keying a canvas?

First time working with a canvas big enough to need keys.  As I understand, they help tighten the canvas, which would be extremely helpful!   It's tight, but sensitive to humidity changes.

The keys keep falling out.

Is there some sort of trick to this?


https://en.wikipedia.org/wiki/Tightening_key

Ah ha!

I put mine in the wrong way, with the slant pointing away from the corrner.



I'm morning how many hours of my life (3) I lost to this problem.