 The glass French doors are typically two doors. They are very weak right in the center. They're typically held just top and bottom by some small pins into the top. Sliding glass doors are even weaker. They are basically large windows which are capable of being lifted out. The sliding portion actually lifts out of the track. Thieves know this. Homeowners usually don't. Thieves are very quick to just get a crowbar into the side, lift up on it,