Why are door locks now installed so that the ridged side of the key faces up instead of down like they used to?

I think it may have to do with which side of the door the lock is on—with most of the doors I’ve run in to, if you’re facing the locked side of the door and the hinge is on your right (e.g., handle is on your left) the smooth side of the key will be inserted up. If the hinge is on your left (e.g., handle is on your right) the smooth side of the key will be inserted down.

Does this match with what you’re seeing?

Kevbo: Are you referring to cars/trucks or house locks? I am pretty dang old (maybe not the oldest contributer, but right up there). I don’t remeber any keys being used teeth or ridges down instead of up any application as the rule. I recall feeling the teeth with my thumb while fumbling to open a door in the dark and the teeth were always up. Some doors and ignitions in cars were used with teeth down, I think Chevys were that way, but I am a Ford guy and the teeth were usually always up. Thank goodnesss they are now reversable, very handy.

Now that I think about it, maybe it has to do (with house locks) as to how they were installed or the brand. Another example: In my house all of the electrical receptacles have the ground plug opening on the bottom where in our church, all of the ground holes are at the top of the plug-in.

I have another Inponderable that really bugs me, to follow later.

@Cardinal: actually the ground-orientation is a relatively recent (~20 year) fad with electricians. Basically, someone figured out that it’s actually slighly safer to install the plugs with the ground lug UP instead of down so that when something metallic falls into the gap between a plug and the socket, the first thing it is likely to contact is the ground, which will then harmlessly short to neutral, or trip the breaker when it shorts to hot.

I’ve heard that in Europe the ridged side usually faces down while in North America the ridged side faces up (or maybe it was the other way round?)

As for the earth pin facing up for safety (though I’ve never seen this), I believe that another further measure is the now mandatory, at least here in Australia, insulation of the top half of the pins which means if something falls down it only touches plastic

Oh, btw, I was looking around my office building today:

Deadbolts seem to follow the pattern I described above, but door knobs were installed every which way.