It doesn't really make a lock more secure but it may restrict key duplication. It makes it harder to duplicate, to some degree and It may also make it harder to pick, or
at least confuse the picker. It can be done to almost any pin tumbler cylinders and is good to fool "key cutters" at the mall or hardware store.
Even a locksmith would be wondering why you have a key modded like that...I certainly would ask questions before i cut it.
There isn't really any good use for them, but I've made them for people that are really concerned about bumping. It does effectively prevent
bumping with conventional bump keys... As long as the bumper is unaware of the device...
Have a look.