I have a 20 year old, wood panel exterior door with a loose bottom rail. It looks like it's sliding off on one side. How can I fix it? If the rail is attached with a tenon I know I can just nail or pin it in place, but do modern wood doors have tenons? or are the just glued together?
Hard to say whether it's a tenon or a few dowels, but assuming the wood is sound, you can pull the rail into place with a clamp (or a strap if you're low on 8' clamps) and put a couple of 8-10" screws through the stile into the rail. (Plenty of skinny long screws these days.) Predrill with a slightly smaller bit. Do a bit of a counterbore and you'll be able to hide the screw heads with filler.
And if you haven't, paint the top/bottom of the door to seal it.