The dark grey 4l flush end axel sits flush with the rectangular block when properly inserted so it's not possible to get a grip strong enough to pull it out of

The dark grey 4l flush end axel sits flush with the rectangular block when properly inserted so it's not possible to get a grip strong enough to pull it out of the grey piece and the light grey piece the red pin goes into has a wall in the middle so you can't push it out through that end. It's impossible to take out non-destructively.