Batt Hold Down clip retention.
 

Bought my car used and never had clips. New clips inbound but I can see a that an encounter with a pothole or bump might cause them to come off. Any ideas how to tether clips to battery tray so the stay with the car ? (Solved) Used small cable, fishing sinkers, heat shrink.

the battery clips are a horrible design. I've always had to fiddle with them to get them to snap on correctly - but once done, I've never had it come off.

Design
 

Thx. I first tried to clip the bottom. No-go. Top first then rotate down.There is no doubt that it's place, loud solid "click" I wonder if it's designed to break away in a crash ???