Commercial truckers use king-pin locks when leaving a trailer unsecured. We used them for years when dropping at terminals that were “dark” (not open/unsecured) all night. I ran one of those facilities for several years. I made a 30”-cube safe out of concrete and a drop safe that you would install in a concrete floor. I made up a set of forms, poured the concrete, then set the safe in the top. The regular driver had a key in his tractor and, if we had a new driver, we gave him the combo to the safe. We keep the spare key to the king-pin lock in the safe, nothing else.
One morning, I came to the terminal and saw that the “safe” was missing. Some yahoo had evidently used a winch and lifted it off the porch, probably putting it into the back of a pickup. I wish that I could have seen his face after he broke through all of that concrete, then cut the safe open, just to find a single key. Sometimes there is justice in life.
Needless to say, we purchased a new lock, with a different key, the same day. I built another “safe” and it stayed there for a number of years.
