Today a customer asked me to put a lock cylinder in a sliding glass door so I got out a Slide-Co SC1 cylinder I had bought for the purpose. Had to rekey the cylinder so I started unscrewing the cap and discovered that the cylinder turned without even having a key in it. When I took the cylinder apart I discovered that all of the top pins are actually bottom pins.
Lazy locksmiths use bottom pins as top pins because it makes nearly every key work when put into the cylinder. If you use one bottom pin as a top pin, nearly half of the possible bottom pins will still work for that chamber. If you aren’t able to picture that, know this: the security of the cylinder is compromised if somebody does this in a few chambers. If they do it in all of the chambers, they may as well not put any pins in the cylinder at all. The cylinder I had would literally open if I used my fingernail.
The other issue with this cylinder: the plug came filed down from the factory. Lazy and inept locksmiths sometimes decide to file the plug in a cylinder down because they are unable to find the proper pins to match the depths in a key, or they want to make multiple keys of different depths work. This makes the cylinder inherently insecure. There are certain situations where I can see somebody filing the plug down to make a bunch of people’s keys work but you shouldn’t get a cylinder plug filed down from the factory. There is really no excuse.
What can you do about this? If you put one of these in your door, make sure that a screwdriver doesn’t turn your sliding door’s lock, and try multiple keys not meant to open that lock to make sure that none of them work. If the lock fails either of these tests, consider bringing the cylinder to a locksmith to fix the issues I have described. The top pins need to be replaced for the cylinder to do its job properly.
A better solution would be to buy a better cylinder. Unfortunately, most patio door and sliding door locks are designed to only work with these terrible after market cylinders. I am still looking for a proper solution to this problem.