I am sure that most of us routinely have access to some sort of FAK, hopefully compatible with our training. Within it most likely there are meds of various sorts, bandaids and sterile dressings, etc.,but nothing too terribly bulky or heavy.

This means that when faced with a really serious injury, we will need to improvise -a bandanna becomes part of a tourniquet- a belt or duct tape holds a dressing in place, etc.

What improvisations come to mind when you contemplate dealing with various serious situations when you are not in quick communication with 911? What are your tips and tricks which will be generally useful?
Sometimes even fully equipped SAR teams run out of supplies. I once took off my pants to complete splint padding (I had a second pair in my pack)....