My condo does not have windows; instead, it has 2 glass patio doors, one in the living room, one in the bedroom, both rather old.
Cold air is coming in under the bottom of both, mostly the bedroom door.
I have put old towels at the bottom of the door, to help with the drafts. I desire a better solution, though.
Remember, patio doors run on tracks.
Replacing the doors is out, financially.
Also, no sealing off the doors completely, please.
Suggestions from HandyDopers?
There is a replaceable piece[s] on the bottom of the ‘active’ half of the unit.
(Active = the half that slides back and forth)
It is a ‘strip’ that slides in from one end or the other.
On the ones that I’ve worked on, IIRC (it’s been quite a while) the first thing to do in order to replace the ‘weatherstrip’ is take the door out of the frame and lay it down so that you can access the bottom of the door.
To take the door out of the frame you’ll have to slide it open about halfway, then pick up on the door and swing the bottom out past the tracks so that the top will then come out of the frame. It would be advisable to have someone help you with this task.
Once you have the door out of the frame, lay it down on some old quilts or ‘moving pads’. You should be able to see the weatherstrips at this point.
On the sides of the door at the bottom there should be a small plate that can be removed. Remove the plate, slide out the old weatherstrips and then just reverse the whole procedure.
Home Depot or Lowe’s might carry the replacement weatherstripping, I’m not sure. If they don’t, then you’ll have to get out the Yellow pages and look for parts there.
If you can post some pics I might be able to give you a little more detailed advice.
I’ll check back in a little while.
If you want you can PM me and I’ll give you my # and maybe I can “walk you thru” some of it.
You can buy self-stick weatherstripping designed for sliding doors. You lift the doors out of the track, apply the weatherstripping, and replace the doors. Ask at your local hardware store.
A vinyl door sweep might solve your problem. Sold on the same aisle as weatherstripping at Home Depot and Lowes. Meant primarily for swinging doors, but one of the styles might work on your old slider.
If you do the weatherstripping yourself, (1) get someone to help, those things are reallllly heavy, and (2) Lay down a tarp so you won’t scratch your floor when you take it out/put it back in. Oh, and (3) do it on a warm day. (Duh.)
I will further caution that my husband and I did this ourselves, and the goddamn door has not worked properly since and probably never will again. It now requires serious muscle and a learned technique to open it. No cold air coming in though.
Not trying to be dismissive, but I don’t think that a vinyl sweep is the way to go.
Vinyl sweeps are designed to be used on “swinging” doors (hence the name ‘sweep’). 
On sliding doors, the weatherstrip consists of a strip that’s about 1/8"-3/16" wide x the width of the door unit, which can vary from 2’ to 3’+, with ‘fur’ or ‘hairs’ protruding from it along the length of the strip.
The strip itself slides into a groove[s] on the underside of the door unit. 
There are usually ‘adjusting’ screws on both ends of the door at the bottom. The adjusting screws are sometimes located behind the small plate, recessed inside of a small hole. After installing new weatherstripping it’s sometimes necessary to readjust the door for proper clearance in order for the door to slide freely.
ETA… When adjusting the door for proper clearance, it can help if you’ll take a ‘flatbar’ and gently lift up on the door (on the side that you are trying to adjust) just enough to take some of the weight off of the rollers, while tightening or loosening the adjusting screw.
Read my last sentence. Thanks 
BTW, I’ve installed scores of sliding doors for Home Depot. The sweep was offered as a possible fix, since one has to give Bosda a good amount of options. 
He might also check for gaps between the track and the floor. Some elastomeric caulk (inside or out) might help if that ends up being the issue.
Wouldn’t caulk screw up the door?
He could also use that to completely caulk both doors shut. That way, he never has to go outside again. Or inside again, depending on what side of the door he caulks last.
Handy no longer posts here.
Come tomorrow, when daylight is there, I’ll get a look at the doors.
BTW–they may date to the late 50s early 60s.
Under the track
Not under the door.
Look between the track and the floor, see if there are any gaps.
If not, don’t worry about it.
My apologies sir, I stand corrected. 
Excellent suggestion, and one I had overlooked. :smack:
Dude, we stand together! 
Your post about the brush type of weather stripping was the correct way to go for someone that is kind of handy. I only added what I did to get someone else thinking outside the box for other possible fixes.
Certain styles of sweep might end being useful. Tho I haven’t done it myself, I’ve seen it used as a “sort of” fix on really old sliding doors. The problem that comes up is it dragging along the track. But some of those really cheap self stick vinyl sweeps have a little bit of a bend (or flare) in them and might just clear the track while still blocking enough airflow.
If the door is so old that the proper weatherstripping isn’t available anymore, a really handy person might even want to try making (with a break and some snips) their own addition to the doors out of some metal coil. I’ve seen some pretty ingenious solutions from some people. I’ve also seen some total crap.
Best thing for the OP to do is to see if the brand of the door is still readable somewhere. Maybe on a plate near the top of the dead side or somewhere on either edge close to the latch. With that brand in hand (and possibly even a model number), do a web search for parts.
As usual on the SDMB, all of this is YMMV.
I still think the best thing to do is caulk him into his apartment, see how long he lasts with no food or newspaper ads.
j/k Bosda!
If you killed his Internet access, my WAG would be approximately .75 nanoseconds!
(Of course, I wouldn’t last much longer than that. ;))
OK, a gap seems to exist between the carpet and the base the track is resting on.
I can’t tell how deep.
Or if it runs underneath the track.
Take a piece of wire that will fit into the crack and see if you can guage how deep it is. I’ll wait for you to check if you’re going to do it ASAP.