Hardwood French doors won't lock

You need to start removing, one by one, the metal plates around the holes to find out what's going on. I would start with those around the bottom bolt holes.

Thanks - the bolts do in fact engage properly, and they're quite a loose fit. It's the one bit that I can see with the other door open. I think the main problem is the claws. The mechanism works perfectly when the other 'non-mechanism' door is open - it's simply that the claws won't fully engage with the doors closed. And I can't see any way to adjust that.

I've had something similar. I thought it was a problem with the claws but found that the bottom bolts weren't going all the way down due to catching on the edge of the hole and rubbish in the bottom of the hole. I've got hardwood doors, so they aren't going to sag in the heat, but if you have plastic doors it might be worth checking the diagonals to make sure they haven't lozenge'd

Yes, there was some muck but I've cleared it. I'll take the plates out - no harm.

They're hardwood btw. There is a 2mm at it's widest difference in the gap between the doors. Not noticed it before, so perhaps the extreme heat has done something.

Our front door has got very sticky. I have yet to determine if the heat is making the door sag (it's 4 planks, 3 cross rails, and no diagonals) or whether it's the frame moving. The porch is timber framed...

Andy

I have a similar problem with ordinary UPVC doors in the heat. Like you there seems to be no wiggle factor built in. It looks, in my case like the frame or door warps in the heat making one or both not quite go fully home.at the moment I have taken the lower latching plate completely off, and now it works, but its hardly a very secure idea!

Brian

My garden door gets very sticky every time it is in full sunlight. It appears to be pure thermal expansion of the wood, since it frees up at night - rather too fast for humidity change.