Thank you very much, bacpacjac!

I know of someone who mended a railway locomotive with duct tape ! An air pipe had split and the this prevented the brakes from being released.
Duct tape alone would not have reliably contained the pressure, but duct tape and cable ties did the job.

My emergency kits each have a small bottle of Break-Free CLP, which is more flexible than WD-40 in what it can do, and conveniently for me is very useful for firearms specifically.

Duct tape is so amazing and so capable that I never go anywhere without it.

Boots soles use a heat sensitive glue. A heat gun will take the soles off so new ones can be attached.

A hot car or a hot campfire will break that bond too.

Seen it several times after a snowy wet backpack. Boots dried by the fire, then next day they start flopping while hiking.

A speedy stitcher or some bailing wire braces will get you back home then.

Clearwater that's a great bit of advice about boot soles.
I had no idea that some boots were not stitched together so I'll check that out before I buy the next pair.

In the old days (two or three decades ago) soles were mostly sewn on. In recent years they're usually glued. It's cheaper (of course) but results in a book or shoe that's more or less disposable.

Yesterday I made a short test walk (about 2 miles) with the newly reglued boots. It was strictly a DIY job, so I wasn't entirely sure about the results.

Well, they seem to hold so far, but I'm not trusting them anymore for a prolonged hike. I guess they also lost their impermeability.

I shall buy a new pair, which is a nuisance, not only for budgetary reasons, but also because I have large soles and I find most boots to tight for me to be comfortable, especially in the toe region.

Generally, I find military and law enforcement style boots more comfortable than "civilan" hiking boots, probably because they have reinforced toe caps, allowing for more toe space.

I'll probably end up buying the exact same model as the old ones...