I recommend trying to get the door off the track before being satisfied with any sort of wooden solution. The sliding door at my buddy's place can be opened when locked simply by planting a hand on the middle of the glass, and hooking a finger in the handle, and up she goes. Then just shove it over a bit (over top of the stick) climb inside, get it back off the stick & clean the freakin window before his mom sees. (actually, this was in high school, so pretend I wrote it all in the past tence)
The way to avoid this was to use a thicker stick. It you do use a thicker stick, make sure you put a groove in it to keep it on the track, otherwise, 15 seconds of jiggling will knock it right off the track.
Someone else mentioned the lock on the back of the door. It works for keeping criminals of opportunity out, but it won't stop someone dead set on getting in. Come to think of it, nothing will, but thats another thought. But the reason why that doesn't work well is because the pin isn't all that long, plus, the leverage you get by reefing on a big door with a little thing on the bottom corner (attached by a couple of screws) is just not proportional. Maybe with two of them (top and bottom).
I'd be pushing for a security system (along with some of these other solutions). Calgary is a great place, but after living downtown for 5 years, I know that I wouldn't want to live in a main floor place, let alone my girlfriend (by herself?). A house would be one thing (see: the rottweiler solution) but a condo is sure to have bylaws against that form of security. The next best thing is an electronic rottweiler.
