Why Left or Right?
Basically i wanted to make it easier for you to understand which key you are buying, especially when looking into a keyway.
for example the standard Yale rim cylinder accepts a 1A key
As you can now see the lowest ward
(the part of the lock that sticks out)
is on the right hand side
This is a standard profile for most common locks and is known here as a "Right" key
The other main profile but not as common is the "Left" key, as before but this time the profile is "reversed"
for example our U-5I key
As you can see the lowest ward would insert into the bottom Left of the key, hence a "Left" key,
aka a "reversed" key or profile
another good example would be the universal padlock set
Side by side you can see the different profiles