A twin jet that I got to fly some time ago has an avionics door that was right in front of the RH engine intake.
That door, if left just unlatched would hang flat. The fact that it was unlocked was then prone to being missed on a walk around.
It was in fact missed on one or two occasions and engine replacements followed.
The fix:
When opened it was to be latched on its hold open arm. This was impossible to miss. If you were the one that took it off the retaining arm then it had to be locked before you walked away. Miss doing this at great penalty!
Me, I still liked to give it a thump anyway.