I cannot remember if I've mentioned it before, but I will (again if that is the case)... Logistics, logistics, logistics.
I've glanced through a few post-apocalypse films recently, whilst looking for something to amuse. I have been struck by the number of times a film production has sloppily used props or vehicles that seem to be straight from the supplier. No wear, no tear - and definitely no sign that the characters don't have access to fresh supplies. Or, to put it another way, post-collapse may provide quite a supply of gear for those willing to scavenge. This, however, assumes certain things, such as there being plenty of an item, having somewhere to keep that item unused - difficult to do, when you're a group of nomadic thugs looking for fuel/food/whatever.
Likewise, the prepper has to realise that once things have been used up - and they will - you have to make your own out of the available resources.
Forget lithium batteries. Lead-acid are slightly better. Nickel-Iron would be good - but getting them pre-collapse is an issue; post-collapse, you'd better have a chemist or engineer on hand who has researched them.
A nail, once they get in short supply, is going to be a luxury. If you can smelt, re-use old ones, good - but...
This is were doing your homework pre-collapse comes in very handy.
Japanese craftspeople have some incredible skills. Of particular note is their joinery, joining two pieces of wood, whether as a box or a building. Before the mid-19th Century, nails were not really used, as iron was rare and valuable enough that they had to come up with a better solution for their situation.
The world, currently, runs on an idea called Just-In-Time, which means that things are produced, or planned to be produced, just before they are needed. In principle, this is a good idea - you don't have stock sitting unused, you need less storage space. In practice, it has been adopted by so many, many companies that it is difficult to find anyone who doesn't. Post-collapse, it means trouble for anyone trying to get things restarted.
It's the old thought about survivalism/prepping - during a collapse, the food stores will empty very quickly. If the supply chain can't restock - people will get hungry. And very, very angry.