The above video is actually an explanation of how to replace a sliding door installation with french style doors but it does highlight the ease in pulling the common sliding door from it's tracks.
I am called upon often to repair sliding doors, that have become increasingly harder to operate. There are multiple reasons that doors can become inoperative, but we will leave that for a later article.
The reason I decided to include the above video here is to highlight the extreme weakness that almost all sliding patio doors suffer from.
You can see how easy it is to lift the door from it's track. When the door is closed, it is usually held locked by just a metal hook. Often that hook is all that is preventing the door from being opened. I have seen many instances where the sliding door is the principle method of surreptitious entry. Often intruders simply use a large screwdriver or prybar/crowbar (found in most automobiles) and lever under the bottom of the door, raising the whole door frame enough to remove the door completely from the track. Even while still locked.
There is a very simple and cost effective measure that can be applied to prevent most sliding doors from being removed in this fashion.
Simply, install a self-tapping screw into the top track, so that the head is protruding enough to allow the door to still slide but reduce the lift, or amount the door can be raised.
Some lock manufacturers include anti-lift pins in their locks to help with this problem, but often the parts are made from die-cast aluminum, which is weak and brittle.
For about 50 cents you can prevent the door from being lifted off it's track.
Many people insert a piece of dowel or length of wood into the track behind the door. While this is probably one of the cheapest and best methods for preventing the door from sliding open, it does nothing to stop the door from lifting up.