Interesting, so civil cargo aircraft don't have tie downs you can use chains with.
Are they designed instead all around pallets with some kind of longitudinal mechanical locks into the floor? As above, do the straps augment these?
The short answer is in post #675.
Pallets or containers (collectively, "ULDs" or Unit Load Devices) are used for most cargo. The cargo floor is designed with rollers, rails, locks, and restraints to accommodate these ULDs and keep them from moving. When the cargo is too large or heavy for standard loading, a specific checklist must be used to accommodate a "floating" load that is not restrained by the built-in locks & restraints. Straps must be used to prevent movement in 3 dimensions, and the load from these straps must be distributed among enough tiedown lugs.