How do you determine bolt depth?

Insert a tool or screw driver into the mounting hole in the electronic device as a depth gauge.

Drill a screw into the mounting hole and pull on it to see if it seems sturdy. If it doesn't move, it's safe to use.

Insert different bolt types in the mounting hole until you find one that seems to turn easily in the hole.

Thread a long bolt into the mounting hole and turn it until it becomes difficult to turn, and then mark the threads of a bolt.